Yes, you are right, Jsgus are watch/clock manufacturers. But they only supplied the windup motor for the device - barograph or whatever it was. And the whole device was made by Lufft - Stutgart. The Jsgus were just subcontractors for one part.
I am not familiar with the Lufft company, however I found their website - the company was established in the 19th century and seeing its current production, it is very likely that it may have produced barographs, altimeters and other such stuff in WW2. That's them:
http://www.lufft.com/