ACN — American Card Number ACN — American Card Number

ACN Specification v0.9

By ACN · Published · Updated

American Card Number (ACN) gives every distinct baseball card a stable, citable identifier. ACC numbered the set; ACN numbers the card.

Version 0.9 · public draft · catalog snapshot 22 Oct 2026

1. Grammar

An ACN has four required segments and one optional segment, separated by full stops:

PUB.YYYY.SET.NUM[.VAR]
  • PUB: publisher code, 2–4 capital letters or digits (§2).
  • YYYY: the four-digit year of issue. For a multi-year issue, the first year (T206 is 1909).
  • SET: set code, capital letters and digits only, at most 40 characters (§3).
  • NUM: the card’s number within the set (§4).
  • VAR: optional variation segment (§5).

PUB.YYYY.SET on its own identifies the set (a registry row). Adding .NUM identifies a card.

ACNs are matched without regard to case. The canonical spelling is the one the catalog publishes, and other spellings redirect to it.

2. Publisher codes

Each issuer gets one short code: ATC American Tobacco Co., GDW Goodwin & Co., GDY Goudey, BOW Bowman, TPS Topps, FLR Fleer, DON Donruss, SCO Score, UPD Upper Deck. The catalog lists 454 publishers in all; see Publishers. New codes are minted once and never reused. UNK is a convention for anonymous or not-yet-attributed issuers, not a company. If the publisher of an UNK set is identified later, a note is added to the record (§7).

3. Set codes

  • Pre-1951 issues use the American Card Catalog (ACC) designation with hyphens dropped: T206, N172, E270-1 becomes E2701.
  • 1951 and later use descriptive tags. Starter list: BAS base set, TRADED, UPDATE, CHROME, FINEST, HERITAGE, STICKERS. Other sets get a short tag drawn from the hobby’s own name for the set.
  • Set codes contain only A–Z and 0–9. New codes should not repeat the year or the publisher’s brand name. Some older codes do, and they stay as they are under §7.

4. Card numbers

  • When the number is printed on the card (on card), the number is used as printed. When it isn’t, the catalog assigns one (catalog) and the record says so.
  • All-digit numbers are zero-padded to at least four digits: 0001.
  • Letter suffixes printed on cards are kept as printed (0076A). Lower-case suffixes (0028a) mark catalog-distinguished printings of one number.
  • NNO with a running number (NNO01) marks an unnumbered card. A ~n tail (0600~1) separates two distinct cards that share a printed number.

5. Variations and the back rule

A different advertising back is a different card, and so a different ACN.

T206 is the type specimen: 5,264 ACNs, not the “524” subjects people usually count. Each back is its own catalogued card. For now the back is recorded in the card’s description, and the .VAR segment stays available for a coded back table later. Poses work the same way: N172 is the type specimen for poses, with 3,969 ACNs.

6. What does not mint an ACN

Grade, certification number, centering, condition, autograph authentication added after issue, and pack freshness. Two copies of the same card share one ACN.

7. Stability

  1. Once published, an ACN is never reassigned to a different object.
  2. Corrections to descriptive fields (player, team, description, publisher attribution) are added as a note on the card’s record. The ACN stays the same, so a citation written today still works.
  3. An ACN withdrawn because the object doesn’t exist is retired and never reused.
  4. Legacy exceptions. Some existing ACNs predate the rules in §3 and §4 and keep their published form, so citations to them still work. In the 22 Oct 2026 snapshot: 14 card numbers with characters other than letters and digits, such as DON.1988.BAS.0100-b.

8. Citation

Cite a card as ACN ATC.1909.T206.0001, the prefix followed by the identifier. Lot lines and bibliographies may add the player and the snapshot date. See How to cite a card for lot lines, spreadsheets and bibliographies, with a builder for any card.

9. Related systems

ACC (Burdick’s American Card Catalog) names sets, and ACN reuses its codes before 1951. TCDB card ids (cid) are recorded on card records as a cross-reference where known. ACN doesn’t compete with or replace TCDB. Grading-company ids identify a slabbed copy, while an ACN identifies the card.

10. Registry vs enumeration

The registry is one row per set (publisher + year + set). The enumeration is one row per distinct card. As of the 22 Oct 2026 snapshot the registry runs from 1886 to 2025 with 19,689 sets from 454 publishers, and every registered set is enumerated: over 1.16M cards in all. Coverage is uneven: some years and sets are listed in far more detail than others, and a parallel or insert that has no set row yet is not in the catalog. Report a missing card or set on the Corrections page.