The stamp on the back says WPMC in the center. I can make out Western Pine M------- Company.
Best I could do. Can't make out the "M" word.
I'm pretty sure it's Western Pine Moulding Company. If so, that is an identifier for the wood/molding used to make the frame, not a gallery or other identifier.
MOULDING MAN Who Khows to set up and to grind and sharpon knives. Steady Job for right man. Western Pine Moulding Co Box 1S4. Phone TO 5-7700. Los Lunas New Mexico