I think this is 50’s. I noticed a screw or 2 that doesn’t look original. Thoughts on overall condition and value if possible. Thanks

 

Case number 2639 puts it with a 266 movement not 268 although I cannot see difference in photos and this could well be a 266.
Can’t comment on dial .
Judging by regulator way over on advance I would say badly in need of service. Does it go?
Check ebay sold items for valuation.