It is not an HP, it is not UPN, it just looks like the first german pocket calculator. And it works.
Click here and get a ZIP with an abstract in Enlish, a description in German, and an EXE that should do on Windouze PCs.
Ciao.....Mike
Dennert & Pape ARISTO, Hamburg, Germany, was the world's largest manufaturer of slide rules (more than 1000 different models, 1872-1978). It is perhaps less known that they also offered calculators (21 models, 1972-78). From 4-bangers to advanced scientific/statistic with hyperbolic functions. Very well made and sturdy. I own two scientific specimens, still operating perfectly. Only disadvantage: they are algebraic :-(
Alas it is not RPN, but(!) - you must see the big advantage - like all slide rules it has no Y2k problem. ;)
Ciao.....Mike