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...
site:mflenses.com 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.