My first engineering job, I actually used one of these, to do R&M calculations, nine digits to the right of the decimal point, for NASA!
Well, to be honest, the one I used was at least electrified! I just saw the handle of that one. Ugh.
Arrrggghhh, the memories. Thank God for computers!
Isn't that a comptrometer? My mom used to run for one for Santa Fe. I've still got one somewhere. I was to dense to be able to use it.
I still have my ol trusty circular slide rule ....