A sophisticated German measuring tool I believe is a GO & NOGO gauge, although I may be wrong, as I am unfamiliar with this item.
it is of heavy construction and was obviously very expensive when new. It came to me with a small lathe, along with several other mysterious items which I was eventually able to identify.
I don't know quite how it works, or even if it works, but it is beautifully made and has a lovely box. It indicates 0.0001 inch accuracy over a range of around 0.5 to 2.0 inches. The box contains what I think is an adjustment tool and two loose pieces of different lengths which screw into a threaded hole in the arch of the body, probably to act as stops for the work piece being measured..
If you can use it and can fix it if it is not working, please make me a reasonable offer and I will post it to any UK address at minimal cost.