A very weird HP48G

[Cristian Arezzini]

Hello,
I recently moved to a new house and I found an HP48 that is puzzling me. It had been misplaced and I have no idea where it came from, but it's in pristine condition, with no sign of ever having been open or tampered with. It still had a $10 consignment shop price tag, with a like-new pouch but no other accessories. There were dead, but still clean, batteries inside.

Anyway, I put in fresh batteries and turned it on. It greeted me with the usual "Try to recover memory?", I answered no, and it gave me a "Invalid card data" message. Weird.
Then I checked the free memory, and it gave me 127856 bytes free.

It's definitely a 48G, it's not just a wrong faceplate (there's no card door on the back). It's made in Indonesia, and has the printed key labels.

Apart from this, it behaves exactly like a GX, the extra memory can be freely used, and I get no unexpected behavior... except that when I turn it on, I always get the "invalid card data" which I can dismiss and keep working.

So, what's this thing? Has it been (very skillfully I'd say, since there are no marks) opened and upgraded internally? Is there an easy way to check what's "attached" to the external ports, that is giving that "Invalid card data" error?

Is there some detailed information online on modifications like this, since I assume it didn't leave the factory like this by mistake?

Thanks,
Cristian