So I have an MM6, with the 'Autospeed' adjustment. My motor has it's drive shaft stepped down - so that the larger size is in use when the juke's playing a 45, but when a 33 comes up, a solenoid lifts the idler wheel to the smaller diameter portion of the shaft, slowing the turntable down.
Now, back when I was having issues with my motor, and was looking for replacements, I came across two different styles -
One, was like my motor, with the stepped shaft.
The other, however, seems to have a 'spring' around the drive shaft, pictured below. (Not my image, stolen from an auction..)

If you look at the top of the shaft, you'll see what looks like a tightly wound wire around the shaft.
What's the story between the two types? Does the latter one not support Automix? Is that a 'modification' or some kind of fix?