Bulova 1967 Accutron Calendar

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.