Micro Seiki MA-505 variants - any oracles around?

There is a lot of confusion over the differences between various MA-505 models.  I can only provide you with what is my understanding and others may correct me if I am mistaken.

MA-505 Mk I - the original MA-505 dynamically balanced tonearm.  A 9" "S" arm w/ copper wiring.  Still very good by today's standards

Mk II - The MkII is am improved version of the MkI

MA-505 Mk III - 9" straight tonearm w/ copper wiring.  It was designed to mate with very low compliance cartridges which were all the rage in the 1980s

MA-505 L - a 12" version of the Mk II tonearm.  I have never seen one that was based on the Mk I but maybe someone else has.

MA-505 S is a 9" MkII arm, supposedly wired with silver wire.  Note: Maybe - I once owned an "S" arm and when I rebuilt it I found that the internal wire was silver-coated copper.  Maybe mine was an anomoly

MA-505 LS is a 12" arm version of the MA-505 S

MA-505 X - a 9" MkII arm featuring a heavier arm base

MA-505 XII - improved version of the MA-505 X.  Includes heavier arm mounting bracket and oil dump mechanism

MA-505 LX - 12" version of MA-505 X

MA-505 XS - 9" MA-505 X tonearm w/ silver wiring

MA-505 LX II - an improved version of the 12" MA-505 LX.  Same improvements as the MA-505 XII

Wow! Impressive knowledge of that subject.  I once owned what was at least a Mk II version and foolishly sold it without ever having used it. I would only add that for the Japanese, "S" is not always an indication of silver wire.  For example, the Fidelity Research tonearms that bear an S suffix are not necessarily silver-wired, unless there is a separate label so indicating.

Wonderful stuff br3098, thank you so much for taking the time to write it all down!
I recently picked up an MA-505X, seemingly in mint condition (time will tell I guess) at a relatively reasonable price, but wasn't entirely sure exactly what I was buying due to the plethora of models in existence and an almost complete lack of dependable information.
I was under the impression that the 505X had silver wiring, but whether or no makes no particular difference.  I've never owned one but enjoy the sound of it a lot in a friend's system, so I decided it was time to check it out for myself.
Thank you once again, I'm most grateful.