Hi.
I have recently acquired a stopwatch Heuer 33.220 Century. In the 1963 catalogue, the "Century" reference seems related to incabloc shock-protection and non-reflecting anodized aluminium alloy cases. Would that mean that each time we meet a stopwatch with a mat black caseback, it's a Century model ? Does the experts have more information about this or is my simple assumption correct ?

33.220 Century

Non Century on the left and Century on the right ?

Thank you. Jean-Pierre