A friend of mine was, like all of us, converting over to digital and didn't need her film camera any more, so she gave it to me. This was about the time I was moving, so it ended up in a box for safekeeping and I just now found it again as I was rooting around for something else.
In the mid-70s there was a big upheaval when Olympus released the OM-1, a full-frame SLR that was slighter and smaller than anything the competition was selling, but was still a quality camera. It's hard to describe now but you can see it if you can actually hold them; the Minolta SrTs, Nikkormats, Canon FTbs, Pentax K1000s all felt like lead bars compared to Olympus's new OM cameras, and everyone scrambled to make their own compacts. Canon introduced its AE-1, Minolta its XD-11, Pentax its ME, and so forth.
Nikon's initial offering was the EM, which I once had and I think is in a box of parts-donor cameras somewhere, and followed it up in the early 80s with this FG. It used E-series lenses and some others (I find Nikon's manual-focus lens system extremely confusing, and since I don't actively collect or use Nikon equipment, I'm not going to kill myself trying to learn it. I have enough trouble keeping Canon equipment straight). And it has quite a system of accessories behind it: two motor drives, a databack, various dedicated-hotshoe flashes. It runs in full manual, program (essentially full-auto), and aperture-priority auto. I've never run a roll of film through it, but the specs are good.
There's a variant of this called the FG-20, which an FG without program auto and no TTL OTF flash metering.
Camera manual: Orphan Cameras.com