Birchwood Casey? I used some on a S&W 915 police trade in I bought. It actually worked fairly well, although some spots needed some fine steel wool before it would take. I can't speak to its longevity, but I was pleased with how it turned out.
Yes, Birchwood Casey. I want to touch up the edges on some black anodized aluminum where the anodizing has rubbed off. I'm talking about a shiny line as thin as a human hair. It doesn't have to be perfect. As long as the shine gets dulled down a tiny scratch like that should become invisible to the naked eye. I ordered the pen.
I've used it. It's not going to replicate a true anodized surface. But it will darken the aluminum. More applications result in a darker color. If the surface is shiny, the result will be smooth and may not match the finish you are trying to replicate. It does hide flaws well.
You can make a bare aluminum finish less shiny/smooth and take color better, if you introduce a strong oxidizing agent first, for example bleach. If you add no color coat it will usually turn to a dull gray.
I have received the Aluminum Black touch-up pen. I sanded the scuff marks with 2000 grit emery paper to smoothen the scuff marks and to remove oxidation. I then degreased the anodized piece with ethanol. Three applications of the Aluminum Black touch-up pen have resulted in the desired result.The finish appears reasonably abrasion resistant, meaning it won't rub off quickly simply by handling. The touched up area is matte charcoal vs the more shiny anodized black finish. Since the scuff is along an edge that catches highlights, the difference in tone is imperceptible to the naked eye. I did seal the whole surface with an acrylic automotive paint sealant which also evened out the difference in finish.