Odd one out.
This one is very much electronic, not mechanical.
Also it is a departure, not an arrival.
Similar to many slide rules, it has some useful information on the back. Not conversion tables, but instructions on the more advanced use of the calculator. (As had the more simple Lawrence slide rules.)
This is an 11C (obviously...), of the 'Voyager' line of scientific calculators introduced by HP in '81. By then, the electronic calculator had well and truly rendered the slide-rule obsolete. Even though it's already 30+ years old, this specimen still works fine. Come to that, it has no dependancies on external 'networks', replaceable batteries, is low power and has no moving parts - it should remain functional for a while still.
There are collectors of early electronic calculators, and especially of the early HP scientific calculators.
Last week I got asked via-via by a collector of early calculators if perhaps knew of or had one of these that I'd be willing to let go of. I had and I was. So this particular specimen has now been passed on to a collector who was looking for one of these :-)