I have a Higgins Model 88 and a High Standard Sentinel that appear to have been made about the same time.
According to John Stimson, High Standard put a coating over the anodizing on the aluminum frames to keep the finish from coming off. The Model 88 appeared to have high gloss paint. Most of that high gloss is gone from my gun. The Sentinel appears to have a dull finish, but it is good.
I had a lot of powder build up on the 88 from a previous owner. I tried many products to remove it without much luck and ended up having to scrape it off.
When scraping around where the barrel protrudes through the frame I ran into weld at the top of the barrel. At first I thought it was powder build up, because the Sentinel was smooth in this area.
What I found out is that you should not use Gun Scrubber or Slip 2000 Carbon Killer on these frames. They will take the coating off the frames of these guns. I also wouldn't use these products on some of the High Standard Derringers have a similar coating.
