To Libby: It MIGHT fit both SLR and DSLR, BUT if it is for a film camera it will not autofocus on a DSLR. It is imposssible to determine which 50mm lens it is as it has no markings available and I have 4 different 50mm lens!
Certain models of digital Nikon SLRs will allow it to auto focus, D90, D7000, D300/300s are a few I know it will auto focus on, and I would be most if not all of the FX DSLR bodies will as well. The D represents the older lenses, where G are the newer AF-S lenses. Hope this helps.