I inherited this from my father, when he passed a few years ago, but he had owned if for as long as I remember. I recall him bringing it out to show quite a few people, from several different fields of expertise, and yet still, I really have no idea to what it actually is. Having worked for many years with fine measuring instruments, I would say it is definitely well crafted, but that's the sum of my knowledge about it.
It opens and moves in quite a few ways, and if anyone would like to see it in those positions, I can get pictures taken of it. Google of every word and number gave me a link to a very old Ebay auction, where apparently someone else had one for sale.
I have gotten, over the years, at least 3 answers to "exactly" what it is. When I go to check, I find out that my sources were less than dependable. Hopefully, given the scope of experience and fields of expertise covered on this board, someone may know.