I have a Nikkor-Q 300mm f/9 lens for sale. This is the predecessor to the M. The difference is that the Q is single-coated.
The glass is in excellent condition. The threads on the filter ring have some damage, possibly due to mis-threading. However, a filter can be screwed in sufficiently to hold it securely. The aperture scale is hand-made. The shutter is in proper working condition. It comes with a replacement Nikon front cap and the original metal rear cap.
Thanks for looking,
Kumar