Used as a protractor, it allows you to divide a work piece.
Instructions

I had an old Atlas lathe with one of these degree wheels on the back of the chuck, used it often and now I miss it. So I made one for this mini lathe.

The 4 inch diameter wheel has a hole every 5 degrees. I designed it with zero-clearance and, as a result, it is conveniently attached by a tight slip-fit over a spindle retaining nut on the rear of the spindle.
The pointer bracket is just a basic pointer-holder at this time. I'm not quite sure how or where I want to attach the pointer thing. A short length of aluminum rod is shown.

Both parts were "test" printed with Afinia default settings (basically medium speed and 0.30mm Z-resolution) and came out better than expected, so that's good enough for now.
The ring's small holes were well defined and surprisingly it showed no signs of warping or of wanting to lift. Perhaps that part is due to the relief I gave it. I did use a raft.

The bracket doesn't need a raft since only a small area touches the build platform, and to conserve filament I did not use one there.
Roughly 30g for the ring and 18g for the bracket.

Since the lathe's gear case cover must be removed to use this device, I used its two threaded attachment holes to bolt the pointer-bracket on with a couple of short 5mm x 0.80 bolts.

These lathes are regularly modified by the factories with slight differences season to season, and there's no telling if this thing will fit anyone's 7X mini lathe, but I suspect it very often will.

[Update]
Metric files have been provided, around Dec, 2016 so... Merry Christmas, Happy holidays