Acquired in a box of parts cameras, along with my Olympus OM-2S, half a Yashica something, a black-body Mamiya 1000 DTL, and a couple more skeletons that are unidentifiable. I used to have a huge early Pentax SLR but I think it went to Pentax heaven.
Olympus was (is) an interesting company. They always lagged behind the big guys (Canon, Minolta and Nikon) for the mass market, so they tended to cut their own niche. In the 1960s, they led the half-frame 35mm (see my Canon Demi) with their Pen series. In the 1970s, they felt confident enough to introduce their own full-frame SLR, which they called the OM-1. But rather than just make a "me too" camera, they engineered the hell out of it and made it smaller and lighter than the competition, but made sure that the quality was there.
The result was a big splash and a controversy over whether smaller and lighter was better or just flimsy; ultimately the others followed the ground Olympus broke.
The OM-1 was a middle-teir camera; they followed up with this professional level OM-2, and again, Olympus made sure they had a compelling reason for people to buy it. The best of the new features was the off-the-film (OTF) plane metering, which many people felt was far superior to the in-camera metering that measured the light off the ground glass in the pentaprism. The OTF metering worked particularly well with their integrated flash unit, which took its reading from the camera meter; other makers' flash units read the metering off-camera. That made the flash particuarly accurate, and even if you took the flash off-camera (but teathered it to the hot-shoe), you could flash your subject and still use the camera's viewpoint for the meter readings.
It didn't hurt that Olympus made sure their optics could stand up against Nikon and Canon; and a lot of professionals bought it. It was successful enough that they upgraded it a couple times. According to a FAQ, the OM-2S model was an extensive redesign and added a lot of capabilities to an otherwise gee-whiz camera.
OM-2 bodies still carry some value, even though a lot of others are being dumped.
Owner's manual: Orphan Cameras.com
Related website: Photography in Malaysia