This watch was my mother's and that is her initials engraved on the back - M.D.C.
The back of the watch has the following on it :
10k RGP Bezel
Stainless Steel Back
I spent a good bit of time sifting through the old advertisement images, but could not find a match for this watch. I think this is another one that falls in between the two date code schemes.
This one is in great condition and still works. It hasn't been worn in several decades.