No way I'd pay $300 for an original FM... although it and the later "FM2" and "FM2n" models, especially, are excellent film cameras. The FE-series were largely parallel with and similar specification to the FM models, though the FE-series was shorter lived.

I bought a literally "like new" black paint FM2n with two lenses and a flash at a local secondhand store for $40. I also have three FE2... one black and two chrome finish. All four are fitted with motor drives. I paid around $40 apiece for the chrome FE2s and $60 for the black one. I wouldn't pay as much for the earlier models, because they have lower specification

The FM was intro'd the final two or three years of F2 production, while the later FM2 and FM2n models were mostly sold alongside the F3. The FM (and FA, FG, FE models) were somewhat more compact cameras with non-interchangeable viewfinders. The more "pro-oriented" F2 and F3 models were larger, heavier and have interchangeable viewfinders (eye level meterless, metered, high point, sports). Most models were available in both all-black finish and with matte chrome top and bottom covers. There were also a few special finishes (see below).

The FM and FM2-series cameras have a built-in meter and exposure can be manually set using "match needle method", but they have no auto exposure modes. (FA, FG and FE series models from the same time frame have various auto exposure modes, in addition to manual. The FG has Aperture Priority and was the first Nikon SLR to have Program AE. The FA has Program, Shutter Priority and Aperture Priority AE. And the FE2 has Aperture Priority AE.)

The original FM was introduced in 1977 and the FE was intro'd about a year later. Both have a vertical travel, metal-bladed, focal plane shutter with 1/1000 top speed and 1/125 flash sync. They can be found in both chrome and black finishes. There was a slight change to the film rewinding crank in mid-production, which some consider a different version. There also was an "60th anniversary" FM model finished in gold. I don't think there was a comparable FE model.

The FM2 was intro'd five years later in 1982 and uses a titanium-bladed shutter with a then-unheard of top speed of 1/4000 and 1/250 flash sync. The FE2 was introduced about a year later with similar upgrades. I think these were the fastest shutters and sync of their day, in any 35mm SLR from any manufacturer. (A Ti shutter was also found in the top of the line Nikon F2 and F3, though both those pro-oriented models had a top speed of 1/2000 and a flash sync of only 1/80. Because of the FM2's shutter capabilities, it was used by a lot of pros.)

The FM2"n" (for "new") was an update in 1989 that uses an aluminum-bladed shutter (same as the FE2), but continues to provide the same top shutter speed of 1/4000 and a flash sync of 1/250. I am pretty sure the FM2/FM2n shutters are electronically controlled (as were FA, FG and FE models, though some of them are lower specification than the FM2/FM2n.)

There was no FE2"n" model.... In fact the FE series was discontinued about a year after the first FM2n was announced. Around 1990 the F90, N2020, N6006 and N8008 models replaced the FE2 (and others) in the N. American market (different model names were used elsewhere). Only the FM series and F series continued in production, alongside the new models.

There also is a rarer FM2n Titanium offered in 1995, toward the end of FM2 production. But the only real difference is that the top and bottom covers are made from titanium that was left naturally colored. It's fairly collectible and one of the pricier models.

FM3A was offered from 2001 to 2005 and was the last of the line. In spite of the series it purports to continue, this model has Aperture Priority AE in addition to Manual exposure mode.

FM10 was introduced in 1995, but really isn't part of the FM series. In fact it was outsourced and built by Cosina using a lower specification, mechanically controlled shutter (tops speed 1/2000, 1/125 flash sync). The FM10 and more pro-oriented F6 are the last two film SLR models Nikon and remain in limited production today. The FM10 reverted to the series roots, though... it only has manual exposure mode. No AE.

My FM2n is fitted with MD-11 winder, which is good for perhaps 3.5 frames per second, if I recall correctly). It's affectionately known as the "AK47 of motor drives", because it's so damned loud. I am pretty sure this same motor drive can be used on FM, FM2, FM2n, FA, FG, FE, FE2 models... and possibly some others. The MD-11 was the first "serious" motor drive for models other than the pro-oriented F-series. There was an earlier Auto Winder offered for the Nikkormat EL (and possibly one or two other models), but it was quite slow... less than 1 frame per second. A later update, the MD-12 usable on the same cameras as the MD-11, I think, though I don't think the two drives are significantly different. I have an MD-12 on an FE2 and don't notice much difference.

a couple of things to remember: the nikon FE was a fully electronic camera. when the meter resistor went south, the camera was operable at only 1/90th shutter speed.
the nikon FM was a manual camera with a meter included. so if the resistor in the meter goes, the camera, otherwise, is fully operable.

having said all that, you'd think the FM was the more popular, but not so, as the FE meter read out was analogue (match needle) whereas the FM was digital. go figure. asked the boys at nippon kogaku why the hell the designed them that way and never go an answer that made any sense. figures...

a couple of things to remember: the nikon FE was a fully electronic camera. when the meter resistor went south, the camera was operable at only 1/90th shutter speed.
the nikon FM was a manual camera with a meter included. so if the resistor in the meter goes, the camera, otherwise, is fully operable.

having said all that, you'd think the FM was the more popular, but not so, as the FE meter read out was analogue (match needle) whereas the FM was digital. go figure. asked the boys at nippon kogaku why the hell the designed them that way and never go an answer that made any sense. figures...