The surprise here is a single square on the maker's test plate that came out looking almost like a mirror. That one sample was not planned, and the maker has openly asked whether anyone can explain it. A mark on metal turning into a polished, reflective patch is a strange and lovely outcome for a parameter test.
The build itself is a rectangular metal plate covered in grids of colored squares, all marked with a 60 watt MOPA laser. To isolate one variable, the maker ran the whole matrix with every setting held identical except the focus height, testing six of them. The grid axes are labeled so the results can be read off directly: one direction runs 1000, 910, 820, 730, 640 and 550, the other runs 15, 21, 27, 33, 39 and 45, and the plate also shows visible parameters such as 20ns, 650khz and 1mm.
What stands out is how usable the plate looks as a reference. Different settings produce a range of hues across the grids, and the bottom section holds larger rectangular samples in metallic colors running from gold through blue to silver. The plate is tilted back and forth so the colors shift and shimmer with the light angle, which must make matching a target color to a setting much easier.
The open question is the mirror sample itself: the maker does not know what caused it. That feels like the most interesting thread to pull on, since whatever happened in that one cell of the matrix could be worth reproducing deliberately. As a reference guide for hitting specific colors on metal, this looks like a genuinely practical piece of test work.