I saw the thread on the Croton bumper auto watch and thought I would throw in this one too. You don't see a lot of them but the Nivada Antarctic GMT is everything as good as the Enicar Sherpa GMT.
Nivada were selected as the USA Antartic expedition watch of choice back in the 50ies, Nivada had developed it's COMPENSATIC, balance spring that was supposed to be less affected by temperature change- the Boffins who selected the watch believed it to be too!
This happened at around the same time Universal Geneve had developed the Polerouter, and interestingly the original Nivada Antarctic watch has Bombay lugs and most often the same hands (daphnie I think they are called?) yet a Nivada Antarctic is UNBELIEVABLY CHEAP! Nivada like Universal kept the name running and models like the GMT Antartic were made. The case is the same size as the Enicar Sherpa GMT and is also a Compressor case same as Sherpa with the bayonet fitment- compressor caseback, a tricky case to open indeed!
I could dig out my original Antartic- if anyone is interested, and take comparison photo's with the Polerouter?.