Yep I thought it was strange also for a custom anniversary rifle for a DU fundraiser. The graver tip broke on the D letter of unlimited made a huge gouge so welder welded the whole word and I filed an repolished the area. Recut and inlayed.It was custom bottom metal and another floor plate was...
Alcoa aluminum was in New Kensington,PA. In the 1940,s to the 1970,s . Might still have a plant there. Across the river from my home town. Anodizing for Aluminum is available in many colors including grey. MTC
Raw AL will oxidize if not coated with something.