These puzzles were made mainly of plywood and composition board. Madmar also made puzzles for Blue Ribbon, Interlox, and Mayfair jigsaw puzzles companies.
Did you ever have a Madmar puzzle? Or one of the other brands mentioned? Or had you heard of them before? These are new to me but I've had a recently revived interest in puzzles since I bought one at a yard sale and began building them again. What fun! Who knew?