From Wikipedia:

Like its predecessor, the FM, the FM2n has a long-standing reputation for reliability and durability.[1] It has an extremely strong body of copper-aluminum-silicon (silumin) alloy.[2] The FM2's film transport consists of high-strength hardened metal gears and moving parts, mounted on clusters of ball bearings. The camera's precision-tapered, high-strength vertical metal shutter blades were fabricated originally of lightweight titanium (later production FM2 shutter blades were made of aluminum), while the mirror/shutter mechanism rides on self-lubricating bearings. The mirror linkage uses the same mechanism found on Nikon's professional F2, with some modern improvements designed to further reduce effects of vibration and mirror bounce. The FM2 also features Nikon's famous close tolerance assembly and minimal space lubrication, meaning that it will reliably operate in temperature extremes of −40 °C to +50 °C.
The Nikon FM2 in black.

The FM2/T titanium version.

The FM2 accepts all Nikon F bayonet mount lenses that support the Automatic Indexing (AI) feature introduced in 1977. The Nikon-made AI lenses of this type are the AF-S Nikkor, AF-I Nikkor, AF Nikkor D, AF Nikkor, Nikkor AI-S, Nikkor AI and Nikon Series E types. Nikon’s most recent 35 mm film SLR lenses, the AF Nikkor G type (introduced in 2000) and the AF Nikkor DX type (2003) will mount but will not function properly. IX Nikkor lenses (1996), for Nikon's Advanced Photo System (APS) film SLRs, must not be mounted, as their rear elements will intrude far enough into the mirror box to cause damage.
During the early 1980s, Nippon Kogaku manufactured approximately 70 different types of manual focus Nikkor AI-S and Nikon Series E branded lenses. They ranged from a Fisheye-Nikkor 6 mm f/2.8 220° circular fisheye to a Reflex-Nikkor 2000 mm f/11 super telephoto. The AF-S Nikkor, AF-I Nikkor, AF Nikkor D and AF Nikkor autofocus lenses will work for manual focus only.
Accessories for the FM2 included the Nikon MD-12 motor drive (automatic film advance up to 3.2 frames per second), the Nikon MF-16 databack (sequential numbering, time or date stamping on the film), and the Nikon SB-15 (guide number 82/25 (feet/meters) at ASA/ISO 100) and Nikon SB-16B (guide number 105/32 (feet/meters) at ASA/ISO 100) electronic flashes.
The FM2 is a mechanically-controlled manual focus SLR with manual exposure control. It is operable without batteries and only needs the two S76 or A76 batteries, or one 1/3N battery to power the light meter, which consisted of an internal 60/40 percent centerweighted system linked to a center-the-LED exposure control system. The exposure control system used vertically arranged +/o/– light emitting diodes (LEDs) on the right side of the viewfinder to indicate the readings of the meter versus actual camera settings. This metering system can be traced back to the Nikkormat FT (aka Nikomat FT) of 1965 and its center-the-needle system. The viewfinder also had Nikon’s standard interchangeable focus screen with various focusing options.
The major improvements in the FM2 compared to the FM were silicon photodiode light meter sensors, limited automatic dedicated electronic flash control and, most famously, a mechanically-timed vertical metal shutter (bearing mounted for reduced friction and extended life) reaching a top speed of an unprecedented 1/4000th second, with an X-sync of 1/200. This shutter was able to reach such ultra-fast speeds because its titanium honeycomb curtains had a travel time of 3.3 milliseconds, half of typical vertical travel metal-bladed focal plane shutters of the time.
The improved titanium-bladed shutter from the Nikon FE2 was adapted to the FM2 in 1984 and X-sync increased to 1/250th second. The new camera was renamed the Nikon FM2n (New FM2 in the Japanese market), but remained marked FM2. The only external differences were the red 250 setting on the shutter speed dial and the N serial number prefix. Advances in metallurgy proved the suitability of high-strength aluminum as a substitute for the expensive titanium used in the shutter, and was adopted for the FM2n in 1989. The only way to identify the different versions is to inspect the shutter—the early FM2n had honeycombed shutter blades and the late FM2n had smooth blades.
In 1993, a special ultra-durable version of the FM2n called the FM2/T was released and sold in parallel with the regular FM2n. The "T" stood for titanium, which was the material used for the top and bottom plates along with the camera back. The Nikon FM2/T listed for $1120 and was discontinued in 1997.