Congratulations, my FM3a is the only camera I've ever bought new as it was just what I wanted. To me it feels only very slightly less robust than an FM2n, but you get aperture priority and TTL flash added and in a very light and portable package. Mirror lock-up would have been nice, but hey you can't have everything! I've no idea how many were made, but I always felt that the production run must have been a bit more limited than others as it was stopped short by the emergence of d***tal.
I purchased mine just after they stopped production and my dealer was able to have the Nikon Rep find one. I started with Nikon F's in the 1960's and this camera and an MD12 performs as good as my orignal F's but with both a completely manual(no batt's needed) shutter and AUTO shutter, it beats the Ftn in operation. My only criticism is that unlike my Fm2, there are no LED's fo manual exposure control and in dim light the match needle can't be seen but I suppose that saves battery power.
In any event its my last Nikon film camera.-Dick