What and why Dunnsville did is mostly a mystery. Most of what we do know about Dunnsville comes from the guns produced there. They produced the 150 for a long time and there are at least 2 and maybe 3 significant Dunnsville variations. Compared to the Fairport model, they're a bit weird or maybe a better word would be 'distinctive.' One of these distinctive only-from-Dunnsville features is a grip frame with non-textured paint.
Why did Dunnsville production include a smooth non-textured grip frame? Venturing a guess. It is entirely possible that they received lots of grip frames from Fairport which were not painted. Dunnsville proceeded to just use regular paint instead of the fancy textured paint. Economy? Availability?