Apologies for veering off the OP's hunt for a MIR, but some other questions popped up in the thread.
I have a '55 J-8 on my 3M, and had a '56 before it. The coatings are hard, "in my Opinion" as good as what is on the Japanese lenses of the day. I've taken apart a 1948 Collapsible Nikkor to clean it, and the coating is hard. Haze came right out. Also took apart the 1955 J-8 to clean and repair it. Sent the 1956 lens in exchange for it, as I was not sure if I could get one back together. These are the tabbed lenses with double-helicals. Turned out that the 1955 lens was missing a screw internally that was causing the helical to slide around and the lens could not focus.
You have to mistreat these lenses to rub off the coating.
The Mir looks like a good choice for a FSU camera. Like any 40~50 year old camera, a CLA is usually in order. And like most of these older cameras, knowing some simple repairs and adjustments is helpful. My Zorki 3M was serviced by Oleg, but still suffered an occasional shutter-jam. This was due to a part jamming up, and some flood-cleaning on the right sprocket was required. I've also done simple repair and adjustments to Nikon RF's and SLR's, Canons, Leica's, and even my old Kodak DSLR. The FSU cameras are not alone in this respect. If you buy a 50 year old Minolta or Nicca Leica Copy, you can expect to have the shutter curtains replaced if they are original. I've got a 1957 Zorki-C with great looking curtains, light tight. My FED 2's did not fare so well.