NavList:

Hi Frank

It's designed to be used on its side, for surveying, I understand.

Eg put it horizontally on a hill top table ( in the UK a 'Trig Point' ), and measure the angular distance to other local features.

Decades ago in the UK, some 'Technical High Schools' taught their 15/16 year olds surveying, and it would have been be just the thing for that job. Mine has a 1980 certificate.

Now completely replaced in practice by the theodolite, I assume.

I have one, same age as yours, pretty much unused I would guess, a 'Kingston' CPlath type W frame in bronze which has a second set of three of legs sticking up from the bronze frame. No idea what advantage is gained by using it 'either side up'.  I've occasionally used it vertically for taking star sights off the beach, just for the sake of using it for something.

Mine is a heavy beast, with thicker mirrors than I've found on marine sextants.  The build quality is very professional, in a great case which by itself is well worth the 50 monies I paid for the whole thing. I thought the pristine mirrors might be useable for spares, but they're too thick or maritime sextants holders. I suppose I could lift off the mirrors complete with the mounting frame.

I keep it for sentimental reasons, my wife's grandfather came to prominence in Co Tyrone, Ireland in a surveying way. He was  a farmer's nth son, and was a maths demon at the local elementary school. As a teenager he solved the problems of local farmers who had to declare the area of their holdings when the land tax system changed. He was known as 'The wee boy with the book', he was the only person in the local area who could calculate the area of the local farmers' fields, understanding the area formulae for irregular shapes in the one top grade maths text book held in the local school.  Noticed by a local church minister, he was sponsored off to Dublin, became a well known maths teacher, and begat a large family in which every descendant has became a university graduate in one discipline or another right up to the current generations. Not bad for a nineteenth century lad from the bogs ....

All the best with your collecting

Michael Bradley