I thought the FM3a was actually a camera designed to show Nikon's prowess as a camera maker, sort of the way the F6 was. The Nikon F6 was a true sales dud; a 35mm film SLR released after the digital SLR had basically all but killed the 35mm film camera, in all brands, the F6 sold exceptionally poorly. The F6 sold so poorly that I have never even SEEN one in real life, either on the street, or at my favorite camera shop, where all types of new and used cameras turn up.
I recall a conversation at ProPhoto Supply, with a sales associate, Karen, around 2003 or 2004. She told me that with surprising frequency, they would have customers who would come in, very much insistent upon buying a Nikon F3. She told me that even though the camera was "outdated", that there were a surprising number of people who fit that mold, of wanting specifically, the Nikon F3. I "get" that.
The thing about the F3 is this: even though it needs battery power to have the full range of shutter speeds, the built-in light meter has proven to be exceptionally rugged. On the other hand, the people who tout the "reliability" of the F and F2 seem to want to ignore the fact that a HUGE number of the light meters in the interchangeable prisms of those two cameras were dead after a mere five to 10 years of use; even back in the mid-1980's, mid- to late-19709's Photomic prisms often had a dead light meter. So much for "reliability". The F3 on the other hand, has proven to be extremely reliable, both in meter and shutter. And even though it felt a bit "flimsy" to me on the manual film advance's feel, F3's seem to still be working pretty well. The integration of the MD-4 motor drive to the body was nice, and slicker, than the old F2 motor system...less kludgy, more modern,more an integral part of the system than an add-on. I dunno...I owned three F2A's and a F2ASb, a rare variant...nice enough cameras, but still, they lacked Aperture priority auto, lacked TTL flash control and flash metering, and had less-accurate, mechanically-timed shutters. As one poster put it, the F3 spanned one era and another era...it was the last manual focus professional-grade (1-digit) Nikon body...at the time, it seemed a bit small, a bit "different" from the earlier F and F2 series bodies, but the design and styling were newer, and better-integrated with modern camera making methods and with the idea of making a RELIABLE light meter that was inside the camera body, and not inside of a Photomic head that was huge and heavy and old-school in styling.
Pro camera repairman Marty Forscher told Modern Photography's Herb Keppler that the F had 974 parts, in total, while the F2 had around 1,500 parts, and that as a consequence of the 50 percent higher parts total, the original Nikon F was _VASTLY_ more-reliable than the Nikon F2. Forscher repaired top professional shooters' gear for well over 30 years in NYC, and was considered the best-known camera repairman in North America for many years.
But back to the FM3a: the Pentax LX of the late 1970's-early 1980's was a contemporary of the Nikon F3. The Pentax had a shutter that offered both electronically timed and mechanically timed shutter speeds. And that was the feature I think Nikon felt they needed to produce in a production camera, just as a way to satisfy their engineering departments pride. Nikon is a company that has a good deal of company pride, and which seems to produce some products that, I and others think, are designed to satisfy senior company engineers, rather than being based on what the camera buying public and Nikon customers say they want. Satisfying internal, Nikon executive "company pride" is why the FM3a and the F6 were released; both cameras came at a time when sales of 35mm film SLR's were very poor.