I've taken apart 3 of these over the last 20 years, the last one about 18 months ago.
You think I'd photograph it up...
It is an easy job BUT you need to have some rubber cork style tools.
This lens is a Tessar formula 50/3.5 in a brass mount with "very shiny Chrome". Performance compares well with the post-war 50/3.5 coated Elmar and coated Zeiss Tessar 5cm F3.5. The I-50 is the third formulation of the 50/3.5 Tessar in the Industar series, it improves on the optics of the...
Very similar to the Industar 50 EXCEPT no spanner slots. I use "Hollow Rubber Corks" that are used to pass wiring harnesses out of project boxes.
I bought the collection of my Friend's late Father-in-Law. The equipment was stored in a safe, that apparently had a high degree of moisture. Included in the collection is a Nikon S4 and Contax IIIa. As received- fungus had started between the cover glass and prisms. The S4 was a 20 minute job...
www.rangefinderforum.com
You can see my typical selection on the above repair thread. The little green rubber cork is what I used for the Canon.