This teleconverter is for Nikon manual focus lenses and bodies and has an AI lens mount. It doubles the focal length of lenses and increases the focal ratio of the lens by a factor of 2. In other words, a 100mm F2.5 lens becomes a 200mm F5 with the addition of this accessory.
It can also be used for prime focus film astrophotography. Attach the TC to the camera body and attach the telescope T-adapter to the TC. I've used it on the Moon with a Schmidt-Cassegrain with great results.
Condition is like new in the original box - no flaws of any kind anywhere.
$75 shipped in the USA. Certified funds or Paypal.