[Leica] Mystery Telesar viewfinder

[pklein at 2alpha.net (Peter Klein)]

Today I was rummaging about in the "used" bins of a local camera store, and 
came upon a near-mint shoe-mount brightline viewfinder. It's a short 
cylinder, shaped very much like the classic Leica 50mm viewfinder.  It's 
black, with the brand name "TELESAR" is inscribed in silver upper-case 
letters on the top of the finder, and a thin silver line runs around the 
cylinder just above the tops of the letters.

The finder has two sets of yellow bright lines, each with close-up marks 
just below the top.  The front of the finder also reflects a yellow 
color.  The view is a bit reduced, and seems similar to my .72x "M" 
viewfinders.  The build quality seems very high.

The lines appeared to be about 35mm and 50mm frames. I thought, "this could 
be useful."  So I took it home, and where I found that the inner frame 
wasn't 50mm after all. The outer frame was just a smidge narrower than the 
35mm frames on my M cameras, but the inner one was somewhere between the 
field of view of a 50 and 75mm.  So I did a little creative viewfinding of 
a tape measure, and came up with the following:

1.  Using the horizontal (long) view of the frame, the wide bright lines 
would match about a 37mm lens (on a 35mm camera).
2.  The narrow bright lines would match a 66mm lens on a 35mm camera
3.  The frame proportions are not quite right for 35mm cameras.  The inner 
framelines have a ratio of about 1.33 or 4:3, the outer framelines have a 
ratio of about 1.4, or 5:7.  Weird that they're not the same.

Can anyone tell me what camera and lenses this finder was made for?  I 
suspect I could use this thing as a reasonable finder for 35mm lenses. But 
perhaps someone has the matching camera and has been searching high and low 
for this finder. . .

--Peter