Bandoneons are datable in one window: Alfred Arnold six-digit serials 100,140–112,625 cover 1931–1941, often with a date stamp on the mounting base. Outer-case numbers were added by importers — and are often forged.
On the mounting base (Montierboden) — where AA instruments also carry a date stamp; outer-case numbers were added by importers. Markings and exact positions vary by maker and era — the serial number guide covers the common locations for every instrument.
4 makers with 204 dating ranges are listed on this page. Coverage grows as more maker records and historical tables are verified.
Recheck the characters exactly as marked — letters and leading zeros are part of the number. On several makes the stamped numbers are internal assembly or importer codes that cannot be dated; some production periods are simply not covered yet.