The number stamps mark gold alloys: 333 = 8 carat, 585 = 14 carat, 750 = 18 carat. They state the fine-gold content. Additional hallmarks provide hints on age and origin. Important: a hallmark (always struck deeper) is to be distinguished from a pure model designation (engraved inscription) — for example a Montblanc pencil model called '10K' existed. As a standard work for determination, Jan Divis: 'Goldstempel aus aller Welt' is recommended. Logos and stars were earlier also stamped into hard rubber and celluloid.