It's all about patina..
Ah Patina! i.e. sun and moisture damage. If you are really fortunate you can have 'mint' and patina!
Patina... Patina? That's a type of Australian potted meat isn't it? Wouldn't want any getting on my watch..
actually those little keys on the side of the tin are really handy for winding things up..
Where as a knackered old Grana is worth every penny they fetch these days ...
There is no logic to collecting.