http://www.nikonchat.com/ais-nikkor/
What AIS and IMP support this objective: nikon 50mm f/1.4 Nikkor AIS IMP?
AI-S is a specific type of Nikon lens mount, it is a manual focus, manual aperture lens that works with any Nikon SLR, film or digital. IMP is not really part of the nomenclature of lens, which means imported. It is a great thing, is exactly the same as any other goal and left the same assembly line, but not guaranteed. Imported, also called Grey lenses market, tend to be a few dollars cheaper than lenses designed for sale in the country where you are buying. There is probably a second list same model the U.S. has in the end, instead of IMP. That would be a guarantee.
45mm Pre-AI Nikkor lens mounts a D700
Nikon News