A holder for a set of adjustable parallels, the text is the size the parallels adjust from and to in millimeters (sorry, i don't do imperial... working in multiples of 1 is hard enough for me at times :)

This is the set i bought and based this on:

https://www.amadeal.co.uk/acatalog/Adjustable-Parallel-Set-3-8-to-2-9-53mm-to-57-15mm-AMA_AC_637_7508TD.html

This item has a wedge shape to it deliberately, it saves a bit of material but mostly it's designed to print so that the top surface is horizontal during printing, allowing for a simple colour change for the text.

When fixing to the wall, omit the center 2 screws, i thought i'd need them for the weight, but they are just a little too close to the rear parallel.