I just purchased a Nikkormat FTn on the bay for a friend of mine who wants to get into B&W photography.The camera has a few issues.Light seals are shot but that's not a problem as I have a Jon Goodman kit.My main concern is with the focusing screen which was described as pretty dirty.What is a "fresnel" screen made of? Plastic or glass?
The FTn screen is non-interchangeable so I must clean it in place.
Suggestions please!

Thank You

I'm no expert on the FTn but I do have one. I'm also pretty certain the top won't come off like the F so you'll have to clean it through the lens mount.

plastic

The Nikon F (and F2) screens of the same vintage were of 2 parts: a glass condenser lens above a plastic fresnel. Without removing the screen, the best method to clean is to blow it off with compressed air.

Back in the day, Nikkormats were considered "stripped down" or "simplified" version of the early Nikon F series of cameras. But the basic "brick" camera body was equal. These suckers will last forever if treated right.

The original Nikkormat was nomenclatured as a FT and the second, and most popular, was the FTN (note the the last letter is upper case). This is distinct from a more "professional" Nikon F version that was, confusingly, labelled as FTn (note the lower case "n").

BTW, I still have my original third series of Nikkormat known as the FT2; and also a FT3!

According to "The Nikon Compendium: "....[T]he Nikkormat FTN would be supplied with one of two different focusing screens: the A-type with a split-image rangefinder or, the J-type with micro-prisms. However, you had to decide which screen you required before purchase because it was fixed in the factory and could not be removed by the photographer. The last series of FTN models was supplied with the K type screen that combined the features of the A and J types."

AFAIK, as the "Compendium" points out, they are not user-removable/replacable.