Should have sent this to you from the start:

All Nikon F finders:
http://www.cameraquest.com/nfinder.htm

General Nikon F history (shows non-metered prism):
http://www.cameraquest.com/fhistory.htm

Enjoy your F!

The first Nikon F cameras (circa late 1950's) had plain prism finders.
No meter at all. Nikon introduced the Photomic F finder, which was coupled
to the shutter and lens, but had a seperate photocell that looked out
from the front. Originaly they had a little screw on telescope which
narrowed the field of view.

In 1964, Nikon quietly widened the mirror box to accomodate larger finders.
Therefore the mirror boxes and internal parts are different from the older
models and not interchangable.

The second version of the finder was called the Photomic FT. It measure light
by averaging the light on the full frame.

The third version of the finder was called the Photomic FTn. It measured
the light from the full frame, but 60% of it's metering came from a
small circle in the center. This is called "center weighted" metering.
The Photomic FTn was the best of the group, there were other improvments
to it.

All of the Photomic F finders use mercury batteries and will not work
properly with Alkeline batteries. They can be adjusted/modified to work
with them. The easiest way is to just reduce your ASA film speed by 2/3 of an
F stop. This will work with everything except slide film, and be pretty
close with it.

Parts have not been available since around 1980 or so, depending upon
what repair stores were hoarding. The big problem is that the meters
depended upon a plastic strip with carbon deposited on it. They were
never kept in large quantities as spares. They are destroyed by useage,
the carbon wears off, like the volume control of an old radio.

One can often get them to work for a while, by rubbing them with a pencil
to replace the carbon. If you do this yourself, it's worth it to keep
an old FTn meter in working condition, if you have to pay $75 each time
for someone else to do it, it's probably not.

At this point, IMHO a mint FTn is too valuable to use, a "user" if
maintained properly will run for many years, but once it goes,
without the meter.

This is true of all the "analog" Nikon cameras, the F, the pre-AI F2's,
the Nikormats and especialy the Nikkorex-F. The Nikkorex-F was NOT
made by Nikon and never sold in the quantites the other cameras
were sold in, and are more valuable due to their rarity.

Note that there was a small amount of F2 Photomic finders made in mid-1977
that were not analog and not AI. Very desirable and rare.

Geoff.