The OM-1n came out in 1979, and is a slightly updated version of the OM-1, which launched in 1972. The OM-1 revolutionized the camera market when it originally came out, due to its incredibly small size for an SLR.
The OM-1n is small (even smaller than a Leica M!), but the build quality is fantastic. It feels extremely solid in my hands. All the controls are at just the right place. I love how both the shutter speed and aperture dials are located around the lens. This means I can adjust both settings without having to move my right index finder off of the shutter. Other features that I like are the mirror lock-up setting (not really necessary for 35mm, but a nice option), removable hot-shoe, and film rewind switch (just like a Leica). The only thing I don't like about the OM-1n is the fact that it takes crappy PX 625 batteries, and not the more reliable 357 batteries.
Here are some photos I took a few days ago on the OM-1n. I used Ilford FP4+ 125 film.
Thanks for looking!