Anybody tried FED 50/f2 collapsible?

I love my 50/f2 summar lens, I am wondering is the FED 50 f2 collapsible similar or different (in a good way)?
Not so may info on the net about this lens.

I understand that they are very rare, and I would suspect very expensive. Cannot imagine that one would be better in any way than a clean Summar.

I had a Summar that John at Focal Point cleaned the haze and fungus out of, and even w/ the etched lines from the old fungus it never flared (with a hood), and was one of the best, if not THE best Leica 50 lenses that I ever owned, and that is comparing it to the 50 DRs, the collapsible Summicrons, etc.

Why not try one of the collapsible 50 3.5 FSU lenses? They're a different optical formula than the Elmars, but image in a very similar way and are a heck of a lot cheaper. You won't have to keep a fingernail untrimmed in order to set the aperture either. The Industar 22 lenses I owned were very sharp.

I've never tried the 50/2 FED, but I have and use the 50/3.5. It's quite good, especially stopped down a bit, and the color rendering is surprisingly vibrant (I would have expected something tending more toward a uniform proletarian gray from the Soviets). More compact than any of the f/2 collapsibles.

If you're looking for something Summar-like, the Canon 50/1.9 seems to be a pretty direct copy of it optically, but with harder glass and coatings.

There has been a FED 50mm f/2.0 on eBay for a while. I think it was about $300.00 US after conversion. Seller was in England. Too much for me tho. I got a really nice Summitar for the same price.

Thanks for replies. I did tried and used Industar-22 (f3,5) - it is a good lens, and I have and use elmar 50mm f3,5 - it is a superb lens. They are different beasts comparing to my clean like new summar (that I also have and love very very much). Because I love my summar so much - that is why I am asking about this unusual Fed lens...