Todays brain bender...

[stan]

if we get it between us , i'll go you halves... but my money is nuts or bridges, heights, slots, shapes, string take off angles

[Crusader]

For removing old nuts?

[vh2580]

Is it for holding a fretboard and marking/ drilling side dots?

[dingobass]

looks like it has about six marks at the bottom and possibly four at the top, something to do with nut slotting/calculating

Nooooooooooooo

[stan]

Depth stop for cutting slots in nuts or bridges

[dingobass]

Yeah, that's what I thought cutting bone to the correct height, length and slotting.

The correct answer is within this answer

[stan]

Cutting/filing nuts to correct height

[wokkaboy]

to get the correct curvature of the top of the nut ie a radius. Wider nuts to the left, narrower nuts to the right of the jig.
DB for the prize do you mean a custom cut bone nut ? MOP might be a bit brittle and expensive !

[stan]

Cutting slots once the curve is done. Nut goes in vertically, moveable piece is an angle guide

[stan]

Dingo claw trimming guide