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I believe I am finished translating the sheets on the top and bottom of the
case.
You can see it all at  http://home.comcast.net/~reneemattie/navigation

I think I have got the sense of the instructions.  I don't mind whether
"the carton at shoulder straps" is something that came with this compass
or a common (at the time) phrase for some kind of backpack or satchel,
though I am curious.

I have never come within 1000 miles of the item, but it seems to be
a standard compass with a decent sight, something like a cross between
a more modern lensatic and a hiker's compass.  It seems to have no
internal dampening.  It is up to the operator to dampen the oscillations
with a brake.  I imagine this takes a bit of skill.  The face is divided
into
6400 parts, which seems a bit odd.  The bearing is read from the map. The
needle is held captive with a brake, the compass is set on the map with the
immobilized needle aligned to the map's magnetic north, the edge of the box
running through the sighted object or the current position, and the bearing
is read from the map.

The compass can be held sideways to measure the incline of a cannon, or to
take the height of a distant object.  This is the altitude part.
One is to sight through the slit stem just as when one is taking an azimuth.
The brass inclinometer needle is then viewed in the mirror.
There is a graph on the back for figuring  slopes (1 in 8, etc.)
as well as height or distance off (depending on which is known).

This is exactly the sort of little puzzle I am good at, I suppose,
and I have enjoyed scraping together my rusty French, some geometry,
and my land navigation skills to figure out the 100-odd-year-old
instructions on this obscure, outmoded, virtual device.

Renee

   

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