Given that the serial number on that packaging (use the zoom view and you can see it) is the same except that if has an extra A on the end, I'd say you've found the stamp. Stacy Stamps has a list of its retail locations
here - maybe you can see the stamp store it was bought at as confirmation? I can't see wood mount on their website but maybe they supply wood mount to retail stores if that's what's requested and use the additional letter on the code to indicate the mounting?