An unusual 48G. What is it?

[Han]

Your HP48G was upgraded to include 256KB of RAM, permanently installed in what would normally be considered card slot 2 of an HP48GX. It additionally has had its 32KB RAM chip replaced with a 128KB RAM chip, for a total of 384KB.

It is quite possible to open an HP48 without leaving a single trace. With practice and knowledge of where the heat stakes are, one can open the calculator without any damage, and similarly close the calculator.