registrar.earth

SF128 Identifier Placement Guidelines

Technical Guidance for Physical Marking of Registered Objects
Draft 0.1 — 2026-02-18
Section 1

Why Placement Matters

SF128 identifiers serve the same function as Vehicle Identification Numbers (VINs), Bates numbers, CE conformity marks, and legal captions: they bind a physical object to a permanent digital record. Unlike those domain-specific systems, SF128 must work across all object categories — from vehicles and electronics to documents, art, and clothing.

This guidance draws from the strongest precedents across all of those domains.

There is no single universal standard for identifier placement. What exists is a patchwork of domain-specific regulations, international standards, and centuries of legal convention — which sometimes contradict each other. This document maps those contradictions and provides SF128-specific guidance for resolving them.

The words "shall", "should", and "may" are used throughout this document in accordance with their conventional meanings: shall indicates a mandatory requirement; should indicates a strong recommendation; may indicates an option left to the implementer's discretion.

Section 2

The Standards Landscape

The following standards, regulations, and conventions inform SF128 placement guidance. Each addresses identifier placement within a specific domain; none addresses the universal case.

Standard / Convention Scope Binding Force Key Placement Rule
ISO/IEC 15459
(Parts 1–6)		 Unique identification of items, transport units, products International standard Specifies identifier format (max 50 chars, IAC prefix, issuing agency structure) but defers placement to application standards. Silent on physical positioning.
GS1 General Specifications §6 Barcode/symbol placement on retail and logistics packaging Industry standard Lower-right back of package for POS items. 32mm ± 3mm from base for cases. 400–800mm from base for pallets. ≥19mm from vertical edges. Picket-fence orientation preferred.
49 CFR Part 565
(US VIN)		 Vehicle identification numbers US federal regulation Permanently affixed inside passenger compartment. Readable through windshield glazing by observer with 20/20 vision at left A-pillar. Capital sans-serif, ≥4mm character height.
EU CE Marking
(Reg. 765/2008)		 Product conformity marking EU regulation On the product; if not possible, on packaging; if not possible, on accompanying documents. ≥5mm height. Visible, legible, indelible. Proportions must match official template.
Hague Apostille Convention (1961) Authentication of public documents International treaty Square format, sides ≥9cm. Placed on document itself or on allonge. 10 mandatory numbered fields. Title shall appear in French.
FRCP Rule 10 Court document identification US federal rules Caption at top of page 1 containing court name, parties, file number, document designation. Content mandated; exact positioning is convention.
SCOTUS Rule 33 Supreme Court document format Court rule 6⅛″ × 9¼″ booklet. Margins ≥¾″. Text field ≤4⅛″ × 7⅛″. Century family 12pt. Colour-coded covers by document type. Docket number at top of cover.
Bates Numbering Sequential page identification in litigation De facto standard Bottom-right corner by convention (from physical stamp ergonomics). No formal standard for method, typeface, or exact position. Prefix + sequential digits.
ISO 7144 Thesis/dissertation presentation International standard Pages numbered consecutively in Arabic numerals. Position not prescribed. Convention: outer edge in footer (double-sided) or centre footer (single-sided).
Section 3

Contradictions and Conflicts

The standards listed above agree on the importance of identification but diverge — sometimes sharply — on the specifics. Each contradiction below is accompanied by SF128-specific guidance for resolving it.

Position Prescribed vs. Position Unspecified

The conflict

Some standards mandate exact positioning — VIN requires readability "through windshield from left A-pillar"; GS1 specifies "lower-right back of package, 32mm from base" — while others deliberately leave position open. ISO 15459 is silent on placement. ISO 7144 states "position not prescribed." Bates numbering placement is convention only.

Why they differ

Domain-specific standards can mandate position because they know the object category. A car dashboard is always a car dashboard. A cereal box always has a back panel. A universal identifier system like ISO 15459 — or SF128 — cannot assume the object's form factor.

SF128 guidance

Follow the ISO 15459 / CE marking cascade model: specify priority order rather than exact position:

1. On the object itself (preferred).
2. On permanent packaging or housing.
3. On accompanying documentation.
4. On a linked digital record (QR/NFC → registrar.earth).

Within each level, provide category-specific recommended zones (Section 5) rather than universal coordinates.

Minimum Size — 4mm, 5mm, or 9cm?

The conflict

VIN requires ≥4mm character height. CE marking requires ≥5mm total mark height. The Hague Apostille requires a 9cm square. GS1 specifies barcode dimensions relative to scanning distance and printing process. These are wildly different scales.

Why they differ

Each system optimises for its specific reading context. VINs are read at arm's length through glass. CE marks are inspected during product examination. Apostilles are read as documents. Barcodes must be machine-scannable at specific distances.

SF128 guidance

Define three tiers based on reading context:

Machine-readable component (QR code, NFC tag, Data Matrix): follow GS1 quiet-zone and minimum-module rules for the chosen symbology. Minimum QR: 10mm × 10mm for casual smartphone scanning; 15mm × 15mm recommended.

Human-readable text (the SF128 string): ≥3mm x-height for direct inspection; ≥5mm x-height if identifier must be read at >30cm or through a barrier (following VIN logic).

Full identification plate/seal (the SF128 circular seal with metadata): ≥20mm diameter for compact marking; ≥40mm diameter for primary identification.

Permanence — "Indelible" vs. "Attached" vs. "Accompanying"

The conflict

CE marking says "indelible." VIN says "permanently affixed." GS1 accepts adhesive labels ("the adhesive used should not damage the item"). Bates numbering is applied on top of existing documents. The Apostille may be placed on an allonge (a separate attached sheet).

Why they differ

Permanence requirements scale with the identifier's legal and safety significance. A VIN that falls off a car creates a safety and theft problem. A barcode label on a retail item only needs to survive until point of sale.

SF128 guidance

Define a permanence spectrum tied to the object's registration purpose:

Permanent marking (engraving, etching, moulding): required for objects where the identifier serves as proof of identity across ownership changes — vehicles, art, high-value equipment. The marking shall survive the expected lifetime of the object (following VIN standard).

Durable attachment (riveted plate, bonded label, tamper-evident sticker): acceptable for objects where the identifier primarily serves the current owner — luggage, electronics, tools.

Removable/accompanying (hang tag, card, document, digital-only): acceptable for objects where the primary identification is digital and the physical mark is a convenience — books, clothing, household items.

Redundancy — One Location or Multiple?

The conflict

VIN regulations require the identifier in multiple locations — dashboard plate visible through windshield, hidden secondary locations on body panels, and a certification label. GS1 recommends barcodes on two sides of logistics units. CE marking requires only one instance. Bates numbering is once per page.

Why they differ

Redundancy correlates with theft/fraud risk and object size. A vehicle is large enough to hide secondary VINs. A consumer product is too small for multiple CE marks.

SF128 guidance

Recommend (do not require) redundancy based on object category:

High-value / theft-prone objects: primary visible marking + at least one secondary concealed marking (following VIN model).

Medium objects (luggage, equipment, furniture): primary marking + machine-readable backup in a different location.

Small objects: single marking acceptable; recommend pairing physical mark with digital record link.

Orientation — Does It Matter?

The conflict

GS1 has strong orientation guidance — "picket fence" preferred (bars perpendicular to the surface the package stands on); "ladder" acceptable on curved surfaces. VIN has no orientation requirement beyond readability. CE marking has no orientation rule. The Apostille is always a square (orientation-neutral by design).

Why they differ

Orientation matters for machine scanning (barcode scanners have directional preferences) but not for human reading or omnidirectional codes (QR, Data Matrix).

SF128 guidance

The SF128 circular seal is orientation-neutral by design. For companion machine-readable codes:

QR codes: no orientation preference (they include alignment patterns).

Linear barcodes (if used): follow GS1 orientation guidance for the surface type.

NFC/RFID tags: orientation determined by antenna geometry and reading distance, not visual convention.

What Goes in the Identifier vs. What Goes Nearby?

The conflict

The VIN encodes vehicle attributes directly — manufacturer, model, check digit, serial — everything is in the number. GS1 barcodes encode a GTIN (lookup key) and may include additional Application Identifiers for batch, date, and weight. Legal captions contain all identifying information in the caption block itself. The Apostille has 10 mandatory fields beyond the identifier. Bates numbers are pure sequential references with no embedded meaning.

Why they differ

This is the fundamental tension between meaningful identifiers (encode data in the ID) and opaque identifiers (the ID is just a key; all data lives in the database). VIN is meaningful; Bates is opaque; GS1 is hybrid.

SF128 guidance

SF128 identifiers are semi-opaque by design — the identifier encodes a registrar prefix and a unique object key, but detailed metadata lives in the registrar.earth database. The physical marking should include:

The SF128 identifier string (mandatory).
A machine-readable encoding of the identifier (recommended — QR code preferred).
The registrar.earth domain or lookup URL (recommended for discoverability).
Human-readable contextual text is optional and application-specific (e.g., "If found, visit registrar.earth/[ID]" for luggage).

Section 4

Universal Placement Principles

The following principles apply regardless of object category. They are distilled from the standards and conventions surveyed in Sections 2 and 3.

  1. The Cascade Rule From CE marking model (Reg. 765/2008)

    Place the identifier on the object itself. If that is not possible or practical, place it on permanent packaging or housing. If that is not possible, place it on accompanying documentation. Always maintain a digital record as the authoritative source.

  2. The Discoverability Rule From VIN model (49 CFR 565)

    A person who knows the SF128 system should be able to find the identifier on an unfamiliar object within 30 seconds, without tools and without disassembling anything. Placement should follow predictable conventions for each object category.

  3. The Survivability Rule From VIN + CE permanence requirements

    The identifier shall survive the conditions the object will normally encounter throughout its expected useful life. Match marking permanence to object lifecycle.

  4. The Legibility Rule From VIN 20/20 vision test + CE 5mm minimum

    The human-readable portion shall be legible at the expected reading distance under expected lighting conditions. Define minimum dimensions relative to reading distance, not absolute.

  5. The Non-Interference Rule From GS1 §6 + Bates numbering convention

    The identifier shall not obscure, damage, or interfere with the object's function, appearance (beyond what the owner accepts), or other required markings — CE labels, regulatory marks, manufacturer identifiers.

  6. The Quiet Zone Rule From GS1 barcode specifications

    Machine-readable components require clear space around them free of other marks, text, or visual noise. Minimum quiet zone shall be 4× the smallest module in the symbol.

  7. The Redundancy Principle From VIN multi-location model

    For objects whose identity matters beyond the current owner, place the identifier in at least two locations — one obvious, one less obvious. Both shall resolve to the same SF128 record.

  8. The Companion Readability Rule From GS1 HRI requirements + legal caption convention

    Where a machine-readable symbol is used, always include a human-readable rendering of the SF128 identifier adjacent to it. A human shall be able to manually enter the identifier even if the machine-readable component is damaged.

Section 5

Category-Specific Guidance

Select an object category for specific placement recommendations. Each entry references the standards that informed the recommendation.

Vehicles & large transport
Primary location
Dashboard plate, visible through windshield from outside (driver's side). If no windshield, a permanently affixed plate on the main structural member.
Secondary location
Concealed marking on a structural body panel — door jamb, engine compartment, or trunk floor. At least one secondary location shall be hidden from casual inspection.
Minimum size
≥4mm character height for the SF128 string (per VIN convention). ≥15mm QR code if machine-readable component is included.
Marking method
Permanent: engraving, stamping, or riveted metal plate. Shall survive the expected lifetime of the vehicle.
Standards referenced
49 CFR Part 565, ISO/IEC 15459
Electronics & appliances
Primary location
On the product itself, adjacent to or near existing regulatory labels (CE mark, FCC ID, serial number plate). Rear or underside panel preferred.
Secondary location
On original packaging or inside battery compartment / service panel.
Minimum size
≥3mm x-height for human-readable text. ≥10mm QR code.
Marking method
Durable: bonded label, laser-etched marking, or tamper-evident sticker.
Standards referenced
EU Reg. 765/2008 (CE marking cascade), ISO/IEC 15459
Luggage & travel items
Primary location
Visible external location in the luggage tag area — the surface a handler or finder would inspect first. Recommend the flat panel adjacent to the carry handle.
Secondary location
Concealed internal location: inside lining, interior pocket, or inside a zippered compartment.
Minimum size
≥5mm x-height for human-readable text (readable at arm's length). ≥15mm QR code for casual smartphone scanning.
Marking method
Durable attachment: bonded label, riveted plate, or tamper-evident sticker. Should survive typical baggage handling conditions.
Standards referenced
GS1 spot label guidance, SF128 lost-item recovery system
Art & collectibles
Primary location
Concealed location on verso (reverse) or underside to preserve the work's visual integrity. For framed works: on the backing board or frame rear.
Secondary location
Accompanying certificate of registration — a separate document that includes the full SF128 identifier, a QR code, and the SF128 seal.
Minimum size
≥20mm SF128 seal on the certificate. Physical marking on the object may be smaller (micro-engraving acceptable).
Marking method
Permanent where the material allows (engraving, UV-invisible ink). For delicate works: bonded archival label on frame or mount. Never apply marking directly to the art surface without the owner's explicit consent.
Standards referenced
Hallmarking tradition, Hague Apostille model (allonge concept)
Documents & certificates
Primary location
Consistent location in header or footer of page one. For multi-page documents: abbreviated reference (SF128 string only) in the footer of subsequent pages.
Secondary location
Not typically required. For high-value documents: QR code on the last page or on an attached cover sheet.
Minimum size
≥3mm x-height for the identifier string. QR code ≥10mm if included.
Marking method
Printed (integral to the document). For existing documents: stamped or overlaid in a non-obscuring location (following Bates convention).
Standards referenced
FRCP Rule 10, Bates numbering, ISO 7144, SCOTUS Rule 33
Tools & equipment
Primary location
Engraved or etched on a flat metal surface, preferably near the existing serial number or manufacturer's mark.
Secondary location
Bonded label inside the carrying case or storage compartment.
Minimum size
≥3mm x-height. QR code ≥10mm if included.
Marking method
Permanent: engraving, etching, or stamping on metal surfaces. Durable label on plastic housings.
Standards referenced
VIN permanence model, CE placement cascade
Furniture
Primary location
Underside or rear surface, on a permanent label or plate. For upholstered items: on the underside dust cover or inside a removable cushion compartment.
Secondary location
Inside a drawer or on the inner frame, if accessible without tools.
Minimum size
≥5mm x-height. ≥15mm QR code.
Marking method
Durable: riveted plate, bonded label, or branded/stamped marking on wood.
Standards referenced
GS1 guidelines for non-retail items
Clothing & textiles
Primary location
On the care label or a sewn-in tag. If no existing label: a separate sewn-in tag at the inside back collar or inside waistband.
Secondary location
Hang tag at point of sale (removable — acceptable as a convenience identifier only).
Minimum size
≥2mm x-height on the sewn label (constrained by label dimensions). QR code ≥8mm if included.
Marking method
Removable/accompanying: printed on existing labels, woven into a custom tag, or on a hang card. Digital record is the authoritative source.
Standards referenced
GS1 fashion accessory guidelines
Books & media
Primary location
Inside front cover or title page verso, adjacent to the ISBN/ISSN block.
Secondary location
Not typically required. For rare or valuable editions: on a tipped-in certificate or bookplate.
Minimum size
≥3mm x-height for the identifier. QR code ≥10mm if included.
Marking method
Printed (integral to the publication). For existing books: bookplate, stamp, or archival label.
Standards referenced
ISO 1086 (title leaves), ISO/IEC 15459
Jewellery & small valuables
Primary location
Micro-engraving on an interior surface where possible — inside of a ring band, reverse of a pendant, clasp interior. Placement shall not compromise structural integrity.
Secondary location
Accompanying registration card or certificate with full SF128 identifier, QR code, and seal.
Minimum size
Micro-engraving: as small as technically feasible (≥0.5mm with magnification). Certificate: ≥20mm SF128 seal.
Marking method
Permanent: laser micro-engraving. Certificate as companion document.
Standards referenced
Hallmarking Acts (UK tradition), CE minimum size exception for small products
General / uncategorised
Primary location
The most accessible flat surface on the object. Owner's discretion; no specific zone prescribed.
Secondary location
Recommended but not required. If the object is large enough, place a second marking in a less obvious location.
Minimum size
≥3mm x-height for human-readable text. ≥10mm QR code if machine-readable component is included.
Marking method
Owner's discretion. Apply the universal principles from Section 4 — match permanence to the object's expected lifecycle.
Standards referenced
ISO/IEC 15459 (format), Section 4 universal principles
Section 6

Marking Specifications Quick Reference

A compact reference for minimum and recommended dimensions of SF128 marking components.

SF128 Marking Dimensionsregistrar.earth — Draft 0.1
Component Minimum Recommended Format
SF128 text string 3mm x-height 5mm x-height Capital sans-serif (per VIN convention)
QR code 10mm × 10mm 15mm × 15mm Error correction level M or higher
Data Matrix 6mm × 6mm 10mm × 10mm ECC 200
Circular seal 20mm diameter 40mm diameter Per SF128 seal specification
Quiet zone (QR) 4 modules 4 modules Clear space, no marks
Edge clearance 10mm from any edge 19mm from any edge Prevents damage from handling (per GS1)
Section 7

Sources and Further Reading