I believe this is a Bulova Accutron Calendar "B". I am assuming the "B" in the "B31167" serial number indicates a model "B".
I believe the M6 date code indicates a manufacturer date of 1966. Rear markings also indicate a 14KT gold case. I believe the wrist band is original. I do not have any of the original documentation or original case. It would have been purchased new in the Dallas Texas area.
It has not been serviced in years. It is my recently deceased father's watch, and has lived in a jewelry cabinet for the past several decades.
I am interested in getting it fully serviced so I can enjoy it on my wrist. Any advise will be much appreciated.