MFLenses has a lot of information on the Russian lenses if you poke around on that site a bit. Search it using google like this... Helios 40

At least for me, google searching sites like that tends to provide better results. I'm guessing that your lens has an adapter on it for Nikon mount?

I have a rather nice Helios 44 58/2 (in M39) and a Tair 11a 135/2.8 (in M42) that I keep meaning to get some time on my Canon. The Helios is a rather neat, very early silver one, SN starting with 00 with the 13 bladed aperture. The Tair is just in great condition and another nice bokeh lens. I need to get some more time with those lenses, they make interesting photos.