Believed to be 1967 Bulova accutron calendar. Backing is inscribed with words bulova waterproof, M7, 1 592064 and my uncles name. There is a maker mark on the case where strap attaches it’s a Swiss hallmark of Helvetia “c”.Inside backing has 6 points of interest #1 203 inside a symbol, #2 18k 0.750 inside a symbol, #3 697 inside a symbol,#4 Swiss Hallmark of Helvetia”c”and very small missed it first time is a series of numbers and letters 3923C496W. The movement has Swiss bulova 218D engraved also top of the inside case is a US pat 2971323ETAL. When I received the watch it had one of those expandable metal bands that I replaced with a new leather band (still have the one it came with but not sure if it’s original to watch)also watch is working and keeps time very well.
Similar to my Accutron Calander, except the gold of course.
We'd ID this as a 1967 Bulova Accutron Calendar (26355)