thanks for the comment. I did not know there was a "III" series! So, I AM missing information, of course.
The "500" Body and Coils are identical in ALL iterations.
The only "audiophile contenders" were the "Mk II Series" (in my opinion).
Their differences reside in their stylus assemblies, in FOUR component parts:
-1- The same "Mk II" Cantilever, with lower mass, and a refined crimp on the tip end.
-2- The same lower-mass Magnet in the "Mk II" series.
-3- Specific compliance units for each of the 3 models in the Series.
-4- Specific tip contours ( EE= 3x7 elliptical), (E= 4x7 elliptical), and (A=.7 conical).
I have no information on a "III Series", though. You're on your own there
And all of this seems like the closing chapter in their history. I think it was Gen. Douglas McArthur who said "Old soldiers never die, they just fade away".
Good luck to you