Squale Watch Sub-39 GMT Blue Vintage Rubber SUB39GMTB.HTB. All the models in the Sub-39 collection are different because each one is inspired by a watch design from the past. The element that unites them all is the case back with a diameter of 39mm, or 40.3mm if Squale watches consider the protruding bezel. All the other features, however, differ from one model to another, from the dial construction technique to the bezel material.