Anyone interested in vintage divers recognize what a Tropic strap is. The others should know that this is a certain type of rubber band, made in Switzerland during the 1960s and 1970s. They were later manufactured in China and Hong Kong too, using the original molds and same materials. The originals are signed “TROPIC” and marked “SWISS MADE” and are typically fitted with an “INOX” or “ACIER” signed buckle. Citizen used the multiple perforated model with a single sliding strap keeper as seen in the pictures below. They are marked “Tropic” and the lug width (let’s say “20mm”) is indicated. “MOD DEP” that stands for “Modèle Déposé” or registered design. The reference no. is also visible on one end. They are made from a very pliable rubber for a comfortable fit and durability. The band is 5mm thick where it meets the watch and on the clasp end and 2.6mm thick at the tail end.
Here it is how a Citizen stainless steel buckle should look like on one of these Tropic straps. My opinion (from the data I have so far) is that most of them came with the “Acier” or “Inox” signed piece.
Not only Citizen were fitted on Tropic straps but Rolex, Tudor, Blancpain, Omega, Longines and many others too. They were all aware of the Tropic quality. Soft, relatively thin, very pliable, durable and a gorgeous feel and look on the wrist. You have a ’60-’70 vintage Citizen Diver? Get a Tropic strap for it! It will be the perfect match!
Read more about vintage Citizen diving watches HERE.