Pete W. wrote:
Thank you for the photos and accompanying explanation. The CTS logo is of the company Cooke, Troughton & Simms. They, along with Baker, eventually became the firm of Vickers Instruments. CTS have a long history in instrument design and manufacture (described in a book whose title I forget - I'll dig it out of the bookcase and post details when I next log on).
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The (almost identical, branded "Vickers") clinometer I have was passed on from my grandfather, a toolmaker who spent WW2 calibrating artillery sights, test-firing the guns and such - if I remember correctly it's for the water-cooled Vickers .303 machine gun[1], for setting the range (elevation / range tables were supplied with the guns) when set up in a machine-gun nest. I've used mine a lot - although my lathe's reasonably rigid on its base (1/2 a ton of cast iron box...), a lot aren't and I've lost count of the number of lathes that I've visited because they "always cut a taper" until properly levelled! By careful interpolation, it's possible to get to within a few *seconds* of angle using the clino on the cross-slide - this works out as small fractions of an inch at 100 yards.. a minute of angle (considered to be "target grade" in the shooting world) comes out to near as dammit 1" at 100 yards...
Dave H. (the other one)
[1] There's a good website somewhere showing the Vickers and its accessories - might tell you exactly what you've got!