I thought the last digit is Year.
At least that's what I've been told by some.
But then others say first digit is year,so...
DOT's were after 1969(?),so they could be 1973 & 78 dates.
I do know your MFG initials are true to that era.
Not like the current repro today showing McCreary MFG.
The do fit the same Format of a set I have here.
