Ron,
I think they're VERY cool...thanks for posting them!

Postmarks can be very helpful when dating postcards; we have many that I wish someone had mailed, so we'd have a postmark. Your top card, though, is a Curt Teich card, which can be dated from part of the number on the bottom right corner .

The first digit is a year, the letter that follows is the decade. Your card is 3A, which translates to 1933. (1A would be 1931, 2D would be 1962, etc.)
A=1930
B=1940
C=1950
D=1960
Sometimes the number code is on the back, or even in the stamp box, but it's often on the front corner.

Keep on posting stuff