Most accordion factories kept no public serial records — but they left evidence on the instrument itself. This is the honest route, the one collectors and repairers actually use.
Badges, medals, titles (“Cav.”, “Comm.”) and “Made in” stamps date a maker’s eras. Paolo Soprani’s badge history is the classic example.
Register-switch shapes, grille patterns and key styles changed with the decades — Scandalli’s switches alone split the 1950s from the 1960s.
Castagnari writes the date under the grille; Soviet bayans carry the ОТК stamp; AA bandoneons hide a date stamp on the mounting base.