Fowler

Fowler's Twelve-Ten

So called because it calculates in both 10ths and 12ths. This is one very classy looking 4" diameter calculator, housed in a watch-type body and made in England.

It uses one scale and two cursors. One cursor is fixed at the 12 o'clock position. One knob turns the scale and the other turns a 2nd movable cursor.

FWIW, I've taken this apart for cleaning and I don't recommend doing it. I didn't realize what I'd gotten into until I had the thing apart.

The two knobs are attached to shafts that end in really tiny pins which have to lodge in equally tiny holes in the hub of the scale/cursor assembly. Due to the fact that this assembly has to be in the circular pan which comprises the back of the device while you're trying to engage the pins in the holes makes it impossible to see what you're doing. So it's a matter of trying to align things by guess and then carefully and minutely jiggling the knobs to try to find the holes by feel. I was sincerely fearful that I might not be able to do it, and finally managed it with a huge sigh of relief.

Fowler's Magnum Long Scale Calculator

Scientific Publishing Mechanical Engineer

This dates to 1900-1907, and is one of the earliest calculators sold by William Henry Fowler after he founded Scientific Publishing in 1898. Records don't show who made this version or where.

Textile Calculator Type B