Check out the first device on this page:
http://puzzlephotos.blogspot.com/

So far, no one has been able to figure out what it is, although some
interesting observations have been made so far.

1) The writing on the front probably says "2/5 de m/m par hauteur",
which implies something to do with elevation or height.

2) The position of the bar on the right side and the pointer on the top
are correlated with the scale. Specifically, when the pointer is at a
number, the bar is at 20/5 of that number. That might imply that there
was a slider that the bar moved, which gave some sort of line to use on
the scale.

3) Someone thought that this might somehow relate to the
weight/length/width of a fish, somehow.

Any of the triviamasters here got any ideas what this device is for?

--riverman