Bulova 1923 6720

I believe we have an early early ladies 18K model.

I have seen at least one other early solid gold Bulovas with the some non-Bulova stamped case with that same M marking.

I believe this to be a "6720".  Date is based off the add as we are pre serialized movements and cases.

Although the dial isn't a match... it numbers are a spot on match for another advertised dial in the same year.