Industar 61 2.8/53mm

Industar 61L/D 2.8 / 53mm bought with the Fed 3 on december 29th, 1989

It is the last standard lens for Fed cameras, since 1977.

What is the real focal length? the more recent versions, on my Fed 5 and 5s, show 55mm.

Industar 61 2.8 / 52mm, bought by Christophe with the Fed 4 on may 1st, 2012

And here is the first version (since 1963). Identical optical formula, but doesn't indicate the presence of lanthanum glasses.

This one is written 52mm; according to J.L.Princelle, some ones show 53mm...