Universal hardness tester - video

Universal hardness tester. By An Engineer's Findings. 34:47 video:

https://www.youtube.com/watch?v=IwmmZozE2EY

There is an easy and quick tool used to approximate hardness in Rockwell scale. A set of Japanese made 6 color coded files ranging 40/45/50/55/60/65 HRC. Slide the test file across the surface to be tested one by one, starting from the hardest file (black-65), if it marks the surface, the hardness of the material is less than 65 HRC. Then proceed to the next file (blue-60), if it does not mark the material then the hardness must be between 60 and 65 HRC. If it does mark the material, then proceed to the next file (green-55), and so forth.

1. I would like to see it disassembled. Is it within reach of an homemade tools bricoleur?
2. It is very useful to know the hardness, as it is directly linked to tensile strength. Unfortunally there is no universal relation between tensile strength and yield strength. Only the latter is a design criterion.
3. Very useful to sort 'anonymous' aluminum stock.