periscope

[PFSchaffner]

Not sure if this qualifies as a tool, since I can imagine all sorts of context for it, none of them entirely plausible -- everything from surveying to submarines, lab equipment to bomb sight. A 90 deg angle telescope, i.e. effectively a periscope; heavy and well made (brass? bronze?); with an interesting reticule pattern that I don't recognize. Clearly meant to be attached to something (the objective end is threaded, and the entire thing apparently pivoted.) Cast into the frame is number 8299681; engraved or etched on the frame is 650-8299680-4. Visible through the eyepiece are a pair of numbers 8299660 and 106-T119E11 (some of these numbers clearly relate to each other.) I'll put a picture of the reticule in a reply, since I haven't yet figured out how to attach two photos to the same posting.

[PFSchaffner]

And here's my attempt at photographing the reticule.

[PFSchaffner]

Maybe answering my own whats-it...

A very similar item is described in this catalog record
from the Springfield Armory museum

http://ww2.rediscov.com/spring/VFPCGI.exe?IDCFile=/spring/DETAILS.IDC,SPECIFIC=13711,DATABASE=objects,

as a sixties-vintage *optical sight for a 106-M recoilless rifle M40.*

And on this site,

http://www.parttarget.com/6650-00-987-3220_6650009873220_8213863.html

the reticule is described with largely
incomprehensible mil-spec language but dated to 1963,
stadia scale, range 200 to 2400 meters, manufactured by
US Army Armament Research for use in an 'elbow telescope'.

So. A tool of sorts, I guess. I thought it had a military feel.

[Bill Houghton]

So it's for shooting around corners?  Cool!

[Plyerman]

Never seen one of those before. Interesting.