My rarest item is a Diehl Alphatronics a very rare combination of computer/calculator it's a same kind machine as the HP 9820A or some Wang calculators from the era (early 70ties). I also have the service manuals for this machine and some spares to keep it running. Other rare items in my collection are the HP 9821A actually a HP 9820A with a cassette drive like the HP 9830. And a HP 9831A which is basically a HP 9825A with firmware to run HP 9830 basic and a different keyboard, but the firmware also works 1n the HP 9825A. I also have part of a memory core module(6 layers) from an IBM 1401.
-Rik
