This belonged to my father

[Batz]

I'm sure there are more than me that remember working out your logarithms before setting up your mill.

[Batz]

.

[thiggy]

Looks like a flight computer.

[johnsironsanctuary]

I'm just at that difficult age-too young for the slide rule age and too old to use a scientific calculator. I can do simple math on a slide rule, but
that 's all the farther I ever got. My dad would wear out a 6" Pickett about every 2 years. Between the slide rule, a pen, a zippo and a pack of L&M's, he wore out the pockets in his white shirts about as often.

[ron darner]

What I can read in the second photo says that it is a trigonometry calculator; around the rim are the various trig functions, and the standardized layout for solving angles, side lengths and so forth are shown in the diagrams.  I'd expect it to find areas, too, but can't make out enough detail.

[Batz]

It used in conjunction with a Sine Bar when setting up angles to be machined on a mill. You could also use your logarithm book.

My kids would have no idea what I'm talking about, and the eldest is 34. It's all calculators for them.

batz