Go to
ebay and put in your search (date, denomination, country). Then go to the "advanced" link far upper right. Then click on "sold items". That will give you all the auctions that have actually "sold" in the last 3 months, not what a person was asking for it. A coin is only worth what you can actually sell it for .. and you can't sell it to a book or price guide. You need someone with a wallet.