Correct me if I am wrong, but this doesn't look gilded to me. It looks like brass. Bill M had one such piece for sale last year. I think he called it EF with marked up surfaces. It is possible that yours and the one BM had last year are the same. Then again, I feel like I have seen this piece somewhere before and I never saw the example Bill had so perhaps it is another specimen.As for the rarity. Likely RR, maybe better. 837 and 838 are usually the ones found in off-metals. 837 being most common in brass, less in copper, least in silver. 838 most common in copper and less common in brass (DH also says both are gilded but I've never seen one.) But 831 in off-metal is more unusual.
My throat hurts just looking at this. I've never gotten into these pieces, but the more I see them, the more I'm getting interested.