Identifying UG bumper

Hi experts, I've been trying to learn a bit more about UG watches and was wondering about this one. It has a 138 SS bumper which seems to be associated with the early Polerouters, although I've seen a few simpler dials with this movement too. The case doesn't seem to have any serial or reference on the case back or between the lugs, seeing that it has the Star Watch Case Co logo maybe it was recased? I don't see any importer code on the movement. Is there any way to get an approximate date for this watch or any extra info?



Thanks for the help and comments!

Definitely a 1950s US import.

I suspect you'll find an HON or HOX import mark on the balance cock - can I see a snippet of the text here?

I must have been still asleep when I first saw it. You're right, there's an HOX code on the balance cock. Nice to confirm it was a US import.

I'm guessing the serial number is related to the case rather than the movement? So it would be more difficult to pinpoint a specific year in the '50s. The radium lume seems in good shape and has caused some interesting burn in the dial if you're into that kind of thing.