SME 20/2 update history

I'm looking to purchase an SME 20/2, and trying to understand the history of the updates and what they did, as in Mk I, Mk II and PP? Also, have there been any updates since 2000?

Finally, any thoughts on the V vs. IV.VI arm?

Thanks for any help anyone can provide.
The MkII has an upgraded motor.
The latest version (as of 9/05) has the upgraded power supply.
I saw an SME 30 with a power supply that resembled a much larger version of the SME 10 power supply with the push buttons. Very chic looking compared to the somewhat clunky older version, I guess the new version is the PP.
YES, check out the enewsletter from stereophile.

"But the allure of a 12" arm was too strong to deter Robertson-Aikman. He extended the magnesium barrel of an SME Series V arm to 12", along with careful sleeving, superb pressure fitting, the right touch of adhesive, and that inimitable SME finish. The result is the SME Model 312S, which probably has the lowest mass of any 12" arm ever made. It can be used with cartridges in the normal weight range of 6-15gm, and with compliances not deemed too low or too high by most makers."

"Moreover, in recent months SME's entire turntable line had seen the introduction of new power supplies that added clever fine-speed adjustment for all three, plus 78rpm and magnetic braking for the Model 10. The new power supply, the bigger chassis, the longer arm, and a bigger platter added up to no mere modification but a new design deserving a new name: the 20/12. "