REVERSE OF MN0976 AND MN0975

These are the reverse sides of two bookmark-style postcards. Note that in the top one (reverse of MN0976), the inscription/instruction reads: "For 1 cent. Postage, Sender's Name and Address only allowed." I guess you were supposed to pay extra to include a message, but...

the sender of card MN0975 got away with sending a message without paying more! (Hard to enforce, I would think.)