How much will a coin be decreased in value due to a defect. In my case, I have a 1860-S 50 cent piece graded by ANACS as "cleaned", but AU-50 details. This coin is one of my "better" coins and for insurance purposes want to give it a somewhat correct value. It's not heavily cleaned (whizzed or otherwise defaced). I'm trying to learn how to post pics on this site, so for now a description is all I've got.
30-50% off the problem free And it depends on how harshly cleaned and eye appeal of the result Not an exact science
USA Coin Book lists it for $600 in AU. Since it has been cleaned, it could be $300. However, it is a key date and if it has good eye appeal despite the cleaning, someone may need it as a hole filler and could pay $400-$500. It's hard to say without seeing clear photos of both sides in order to determine the degree of cleaning. If it was lightly cleaned, that will retone over time, and if it was harshly cleaned then you are $300 or less.
2026 Red Book has at $525. The value would depend on whether or not the defect is a mint error or damage? If you have a pic, place it in a file or app and upload it to your post. Good luck.
I know this is outside the scope of your request, but, I can't help it when I see dollar signs flying away from a wallet.... Frankly, insurance for collectibles is brutal and most insurance companies will not be equipped to give you fair valuations or pay out claims as you would think. Hugh Wood is the primary insurer for coin dealers and the like. Frankly, if your collection is under $50,000 or so, insurance is honestly probably not worthwhile.
If the Red Book is printed (yearly?), I prefer a coin listing that keeps up with the current values. Printing new values once a year is pointless in today's changing PM and coin value environment. It's still 2025 and the 2026 Red Book is already behind the times. While the Red Book used to be the gold standard in coin listings, it's not anymore. (To me.)