This is an English puzzle that was sent as a birthday card. I guess the mail system back then was a lot more forgiving (not automated?) since this is really thick. The puzzle is made of wood and is about 3/8" thick, not counting the outer mailer.
The outer mailer is heavy stock paper that folds around the puzzle and has areas for writing return and destination addresses, and placing a stamp.
The company is Valentine and Sons Ltd. of Great Britain, and they did several puzzles for Alice in Wonderland's original release. Interestingly, all are wooden, I guess that was their specialty. There is a penciled price on the back of this one, 1/6 (one shilling sixpence) which works out to about 20 cents in 1951 dollars.