Add new comment

A filled crown would be normal, but this is not a normal watch. There is no such thing as Platinum fill, so the crown would have been solid. 

Platinum is commonly alloyed with Iridium to make the metal 'Whiter', otherwise it can tend to look too much like stainless steel. 

Another common alloy for Platinum would be Cobalt, but this gives a faint bluish tinge, in which case the metal is then usually plated with Rhodium.