A report number is the unique alphanumeric identifier assigned by a gemmological laboratory to each grading report, certificate, or document it issues. The number functions as the laboratory's internal reference, as the public-facing verification key, and — in the case of inscribed diamonds and some inscribed coloured stones — as the physical link between the document and the stone itself. Every reputable laboratory operates a verification portal at which the report number can be entered and the corresponding report retrieved or summarised, providing a primary check against forged or altered documents.

Format conventions across the major laboratories

GIA reports use a ten-digit number for diamond reports and identifying-format numbers for coloured-stone documents. AGL, Gübelin, SSEF, and Lotus Gemology each use their own internal formats — Gübelin reports typically begin with a two-letter prefix and a multi-digit serial; SSEF uses a similar prefix-and-serial convention; AGL uses a numeric serial without a prefix. The format is recognisable to specialist users and provides a first-pass authenticity check independent of the actual data on the report.

Diamond reports from GIA, IGI, HRD, and other major laboratories are commonly accompanied by laser inscription of the report number on the diamond's girdle. The inscription, typically 100 to 300 micrometres in height and visible under 10× magnification, ties the physical stone to the document and provides the strongest practical assurance that report and stone correspond. Inscriptions on coloured stones are less common but are offered by GIA and some other laboratories for significant pieces.

Verification practice

Every reputable laboratory operates an online verification portal where the report number can be entered and the report contents retrieved or summarised. The major portals are at gia.edu/report-check, ssef.ch/verify-a-report, gubelingemlab.com, aglgemlab.com, and lotusgemology.com. Best-practice trade procedure on receipt of a report is to verify the number against the laboratory portal, confirm the listed weight and dimensions match the physical stone, and where possible verify any inscription on the girdle.

Forgery and alteration of laboratory documents is a known and recurrent problem in the trade. The verification portal — combined with the inscription on the stone and the physical security features of the document itself (microprinting, holographic elements, secure paper) — provides the practical defence. The trade press and the laboratories themselves regularly publish examples of forgeries and alterations, and the verification habit is part of basic trade hygiene.

The report number and laboratory liability

The report number identifies the specific document and the specific examination. A laboratory's opinion is valid only for the stone examined at the time of the examination; subsequent treatment, recutting, or substitution can render the report no longer applicable to the stone presented. Verification confirms only that the report is genuinely issued by the laboratory and that the data on the document matches the laboratory's records — not that the stone now presented is the same stone the laboratory examined.

For high-value pieces, the trade convention is to re-submit the stone to the original laboratory periodically, particularly if the stone has been re-set, re-cut, or shipped through high-risk supply chains. The laboratory issues a fresh report with a new number, and the chain of documentation is updated accordingly.

Counterfeit reports and the trade response

Counterfeit reports — fake documents bearing legitimate-looking report numbers but corresponding to no real laboratory examination, or genuine reports altered to reflect different stones or different grading data — circulate periodically in the trade. The major laboratories cooperate with the police, customs, and trade bodies to identify counterfeit material, and public-warning notices on the laboratory websites identify known counterfeit number ranges and document features.

For dealers and retailers, the practical procedure is to treat any report received in connection with a transaction as requiring verification, regardless of who supplied it. A telephone call to the laboratory or a portal lookup takes minutes and identifies almost all counterfeit material at the point where it can still be challenged.

Further reading

• GIA Report Check — verification portal
• GIA Gems & Gemology — laboratory practice articles
• Lotus Gemology — report verification