I found this at a yard sale last weekend and am having a difficult time finding anything similar to help ID this vintage E. Gubelin Lucerne. The case diameter is 28mm without crown. Crown appears to be aftermarket. Case back reads, "L.P. McGillen Princeton NJ." It is also marked Gubelin Swiss.
It appears the serial number is 8507. I have yet to open the case back to peek at the movement.
I am guessing 40s. Possibly military?
Any help would be greatly appreciated.