Ever heard of an HP 44A (71B look-alike)

[Jurgen Keller]

From Gary Friedman's book "Control the world with HP-IL", page 7:
"The HP-71 is a rather deceiving machine. It was originally designed to be a more powerful replacement for the 41 (it was originally called the HP-44), and I guess that during the development process they just got carried away. ..."

So my guess is that this is a prototype of an HP-71. A very nice and interesting find!