Not many people in general ever knew that the M-IV existed. In all honesty, Dev, I think it was a failed model that never got launched or put into full-on production simple because there is so little info out there about the M-IV, and there are next-to-no photo on the internet of the Standard or Deluxe versions. (I mean like real, actual photos of a physical guitar out in the wild.) It's got the Steinberger Jam-Trem and the old-school Steinberger 40:1 gearless tuners (same ones that were on the Steinberger GS models at the time).
If you keep your eyes peeled, you can snag one of the 2013 M-III reissues at a good price. There actually is a blue one on the Guitar Center used site right now that is priced fairly low, and it has also been sitting up for awhile, which means the store might negotiate if you shoot 'em a call.
Yep also look for the les paul (mostly studio lites) with m3 setup i had 4 sold one
Really love the hsh setup
Slim taper neck, super light, and the chromyte (balsa relief) is very responsive to all pickups ive tried in em
Just a tidbit of info ive picked up along the way.