
What it is is a Gunner's Quadrant and is used to lay or aim a piece of artillery. These things came in a numver of variations thought the basic operation is the same. Assume you want to hit something, say, 2000 yards away. You, being a snowflake would be triggered by the word "hit" and would retire the the boys/girls room to have a good weep. The rest of us would say "what are the characteristics of the ammunition that we have/are using?"
Think about it: for a given round (projectile nd powder combo) an elevation of a given amount will result in a distance that is sorta predetermined. Forget atmospheric pressure (

With a bloody Gunners Quadrant!!! Tell me you knew where this was going, please.
So a quadrant can work in a couple of ways. One is to have a scale with a measure of elevation (often degrees in older models). You would then set the degrees for the distance that you want (for the ammunition that you have),elevate the piece till it matches that number, pull the lanyard and watch what happens. There is actually a bubble level on thse things that will help in the process.
The thing I bought is different. Look at the scale

That does not look like degrees (or mils, the other way of measuring elevation) it looks rather like distances. Yards maybe? I don't know. What this suggests is that this thing is purpose built for one specific round. A round whose ballistics (coupled with a specific artillery piece) will be reflected in the settings of this quadrant.
How does this one work? Well, It would be attached to the piece, the distance would be set by turning the knurled screw on the bottom under the scale until the pointer move to the correct setting. The tube on top is a 1X telescope with a cross hair. You would elevate the piece till the cross hair was on target. Then pull the lanyard etc.
I believe that this piece is Swedish (or Icelandic but that is a stretch). Note the adjustment screw for windage (left and right)

If they were good christians the letters would be "L" (for "Left") and "R" (for "Right"). "H" and "V" are unnatural. If one pokes around one will find that the words for left and right in Swedish can be abbreviated with those letter. Hence Swedish. Stupid Icelanders don't count.
How old? WW1 era maybe? The telescope is marked "Voightlander" which was founded in the mid 18th century. The engraving looks modern to my eye. Then again, the design of the thing would allow for a scope of ~1" diameter by any maker so who knows.
There are a couple of interesting features which I will not tempt fate by boring you with.
I have a handful of quadrants going back to the 1800's, this is the only one with an integral scope though.