I've not heard of anything like this, either. I would agree and say that I also think it's just a case of somebody gluing a POTF coin onto a ROTJ card. I'm pretty sure it's not factory made simply because the POTF coins started with the POTF line, which came after
the ROTJ line. So, the coins, in theory, were not even being produced when this card was made. Also, what cardback is it? It's not a 48-back, since that would have the Nien Nunb offer on the front, so it's a later version of the ROTJ series (65, 77 or 79). Basically, looks like a kitschy custom.
Kinda neat to have, though. I wonder how the coin is attached?