10K White Gold Filled - M5 marking on case back and movement - 2590 stamped on case inner plus watch maker servicing marks. Silvered dial with diamond markers with exposed balance.
Wow, this one is interesting! Can you confirm date code on movement? It looks to me like it might be "L1"?
Pre 1967, this watch with a matte finish dial with no cutout was a Beau Brummell and post 1967 was renamed Diamond Excellency.
The skeleton polished silver dial is something I have never seen. My initial gut reaction is that this is a "one off" jeweler modification of the dial.
In reply to Wow, this one is interesting… by neetstuf-4-u
The case and dial are Beau Brummell like this one although I think it only came in 17 & 21 jewel movement. I'd tag it 1965 Bulova Beau Brummell without a variant based on a possible 23 j movement. It appears the dial has been polished but configuration is original I think
