Anyone know what this is for?

[Canon Junkie]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=12581&item=3879899148&rd=1&ssPageName=WDVW

Wondering if it has photographic applications of any sort... made by Leitz.

 

[Stephan]

For the rangefinder equivalent of a coloscopy ?