One more JSP adjustable mill close to 15 years old cranked with a 18VDC drill. To get a uniform grind and a boost in efficiency, I've gone to a double grind. I set the rollers (eyeball) to get a light crush for the first round, then tighten the gap (eyeball again) to get a more uniform crush. This helps when using malts of various kernel sizes.
One note, there is a risk of stuck mashes if you mill too fine, but that's what the eyeball is for, so you can get it just right.
Only complaints about the older model JSP is the small hopper and breakable O-ring that drives the second roller.
If I ever had to replace it, I would go with a three roller adjustable mill.