Nikon is rightly proud of the longevity of their F-mount. Since 1959, the bayonet mounting system for Nikon SLR cameras has remained the same. However, the communication system between the lens and the camera has been re-designed several times. The original system, utilized by the F, F2, and Nikkormat cameras, used a large prong on the camera that locked into a bracket mounted on the aperture ring of the lens (often called "bunny ears").
The later Nikkormats, and nearly every Nikon camera since the late 1970s, use the Auto-Indexing (AI ) system. It performs the same function, but uses a very small tab on the camera body, which couples with a raised bump on the back of the aperture ring.
The older lenses, though, didn't have the bump. Or more accurately, the entire ring was raised to the height of the bump, but there was no lower section for the camera's tab to fit into. In many cases, mounting an older lens would break off the AI tab, and the camera would need extensive repair to work again with any lens.
A much more attractive option is modifying the lens for compatibility with both the old prong system and ALSO the AI system. This involves removing material from the back of the aperture ring, but leaving it in exactly the correct place to allow for accurate light meter operation.
At LeZot Camera Repair, we have been performing this modification service for 30 years. Please let us know which camera(s) you will be using the lenses on, so we can allow for the f/min switch.
Below is at least a partial list of AI camera bodies:
D1 D1h D1x D2 D200 D2h D2x D3 D3s D300 D300s D700 D7000 EM F100 F3 F4 F5 F6 F601 F70 F801 F801s F90 F90x FA FE FE2 FG FG-20 FM-10 FM-20 FM FM2 FM2n FM3A N2000 N2020 N6006 N70 N8008 N8008s N90 N90s Nikkormat FT3.