The focus seems fine. Am I seeing missing vertical lines in the R and the B?
You may get a sharper image (picture - for discussion) by setting the aluminum tag on a flat surface that the auto-focus will not overthink and apply corrections to.
Some black paints contain a high temperature metallic (Spinel) pigment that comes out gold when over-burned. Softening the focus may help.
i would set the focus dot properly on the tag, then make attempts at softer focus by adjusting the laser head away in half mm increments to see if the results come.