Welcome to the Forum. That revolver is a $400 to $500 gun all day at auction. It is not possible to determine percent finish remaining with pictures, but as a guess, I see over 95% nickel, probably higher. Our best resource claims a plated 38 Perfected is worth $600 in 95% (Excellent) condition.
What you have going here is high condition, an uncommon gun to find for sale, and a top-break that will easily handle modern 38 S&W ammunition. Negatives are that demand is not high, it is classified as a modern firearm by the BATF, and is not a popular caliber.
With a little elbow grease that gun would polish up to look brand new and at auction could bring top dollar before seller's premium. Personally, I would suspect between $500 and $600 is reasonable to expect.
The major problem with this style gun is that, while many people are familiar with how a top-break opens, almost no one is familiar with how the Perfected revolver opens and I have seen many that have a bent quill from trying to force the gun open by releasing only the top latch. I picked up one that was in pristine condition with that problem a couple years ago and fortunately was able to re-align the cylinder quill so the gun function perfectly again. Paid $450 for that one at auction with auctioneer disclosure that it was a parts gun only. Had several bidders interested, so the value is solid for this model. Here is my 1911 shipped gun all cleaned up.