Plenty of information available about the Polerouter. Pro and con. 17 to 28 jewels. Fine cases. Generally good reputation. I have the 215 17 jewel I guess first model. 1957? Very plain but seems to be fine quality and properly functional. Do not know of water resistant version. This one has screw on back with gasket and wrench flats and a nice thick curved edge glass original back. Maybe just a display back option? Never saw a 50 year old original glass back w.w.