On Thursday, October 29, 2020 at 2:16:14 PM UTC-5, Charles Gosse wrote:
I have a 1918 German barograph, photos are at the URL below. It appears complete but I do not know how to make it work. Apparently it has to be wound-up. I also have a photo of the underside of the metal tray, if you need to see that.

https://www.aeroconservancy.com/flugzeug
That's the kind of device you'd expect hanging above the basket of a hydrogen balloon. A precious piece of aviation history!