INDUSTAR 69 - 28 mm / 2.8 (Rare or Prototype?)

Industar 69 lens for Chaika II camera.

So far I have only seen three Industar 69 lenses like this one.

This lens is longer than the classic Industar 69, in fact it is approximately 24-26 mm. long. It also has the following diaphragms: 16-11-8-5.6-4-2.8. The focus ranges from 1 to 3m. There are neither other distances nor is there the infinity indication.

I believe that this is really a prototype lens.

Might the optical scheme be similar to Tessar?

Lens n. 20815

Made in 1967 – 1972 ?

Antonio Savini