It's a factory Polaroid adapter for one of their cameras. I think it converts a Polaroid camera from using strictly Land Film to any 2x3 sheet or 120 roll film with Graflok ease.

BTW, my internet search found nothing. I'm asking because some dedicated Polaroid folks might want these. I have at least three of them. Maybe I should join one or more of the big Polaroid forums and ask there.