Is This A Compass London 1916 Francis Barker & Son

Hi,
Trying to determine if this is some sort of compass or what it could be. 6" in length, marked on the side F Barker & Son London II No 2466 (not sure of the numbers) 1916; the box has 272 on the end. There is a groove on the base so this slides onto the lid.
Barker and son made scientific equipment, not finding this one.
Any ideas appreciated.
thanks for looking.

 

It's military, with that broad arrow. I think some kind of level, but I'm not convinced it's authentic, there's a lot of repro Barker around.

 

Curious to know what this is. Don't think it can be a compass because the range of movement is too small. I wonder if the three stamped lines indicates British military?

 

Yup, British military - War Department, to be precise.

 

Thanks folks! What 3 stamped lines?

 

Ok, I figured it out. The mark I thought was an arrow is the 3 stamped lines mark.

 

Looks like this is a Trough Compass, scroll down the page in the link. http://www.mathsinstruments.me.uk/page60.html

 

For military sketch maps, so they all agree which way is north.

 

CX and AF are both correct. Often used on a plane table, used by military cartographers etc.