The Hamilton 600 Super Compressor dual-crown dive watch with date is a 1960’s vintage dive watch with a new (for it’s time) method to waterproof a watch.
The seals and the caseback are spring loaded so that increased pressure, as the watch would encounter while diving, makes the seal tighter to prevent water incursion. There are limits to the design, and the 600 in the model name indicates the maximum depth Hamilton was willing to advertise.
It’s not recommended that you dive with a watch of this vintage, there are newer watches with a deeper rating – but in my mind newer isn’t necessarily better. This watch has patina on the dial and hands, the case is in excellent condition. After a service on the movement and an unsuccessful search for another date wheel, the watch is as you see it here.
The dual crowns are pretty much a giveaway to the compressor design; the second crown is used to rotate an inner bezel for a second time zone or to time dives. A crosshatch pattern on the crowns will seal the deal as a true super compressor design.
There aren’t many of these around, and this one is a keeper.