If it has 50,000 original miles the chances of the ET dying are low I'd imagine... They are pretty tough. If it's just a solid color (probably red?) with a 50th anniversary badge slapped on the front fender, it isn't a 50th anniversary.
Some visual differences between the actual 50th AE's and the "normal" 300ZX's were:
The most obvious, two tone paint job as you can see above.
50th AE emblems at the top of of both the driver and passenger seats (Leather)
Turbo finned wheels, 16", with gold "inserts".
And of course, the 50th AE emblem on the driver's side fender.
The interior should also have two knobs that control the "Bodysonic Amplifier" in the center console, that's one key difference in the interior.
If the one you are looking at doesn't have all of these, then it most likely isn't a 50th AE.
k its not i guess it just has the badges. nonetheless an 84 with 50000 original miles damn i'll put a turbo in it. its actually that color grey but it has 15's no two tone and about the interior i couldnt tell you