My father-in-law was born in Germany. He has an extensive German coin collection, some worth thousands of dollars each. He's collected his whole life. He's always collected the best. Now that he's in his late 80s, he's trying to sell some coins to make ends meet. Trouble is, no one is willing to pay close to what some of these coins are worth. Buyers admire his collection, but tell him if they bought them from him, the coins would sit on their shelves forever. He's tried eBay and other on line sites with no offers. I know you're supposed to collect what you want, but is strictly buying rare foreign coins a bad decision? Usually, at least one time in your life you're going to have to sell some. If a coin's worth $5,000 and no one wants it, it's only worth melt.
Honestly, it sounds like a situation many ancient collectors get into. Trouble is that his is a specialty collection, and local dealers will not have much of a market for it. You really need to have him talk to an auction house that specializes in the types of coins he collects. Do not mess around with Ebay or local dealers if he truly has a special collection of items that are higher end and more specialized than most local collectors would know about. In such situations always talk to specialty auctioneers. Heritage could be a start, but there are other world coin firms as well. Maybe someone more into modern world coins would have a better suggestion.
I would check with Heritage as mentioned. Like you said a coin is only worth what someone is willing to pay.
According to PCGS and the opening of their Foreign Offices in Paris and Hong Kong, World Coins is a fairly HOT Market. My advice would be to have the known rarities graded and encapsulated by PCGS for possible inclusion in a Heritage Sale which is made up solely of World Coins. As a general rule, collectors of US Coins have little to no need for World Coins. As such, the OP needs to address World Coin Collectors. It might help to go to the World and Ancients forum ( https://www.cointalk.com/forums/world-coins/ ) for valuation assistance.
No, there is none but there are several German language forum sites around: numismatikforum.de, muenzen.net, muenzauktion.info, numismatik-cafe.at, muenz-board.de and probably more. Except that this will not be very helpful for somebody whose collection is in the US (I assume) where the number of possibly interested buyers is very small. If the collection was in Europe, I would suggest Künker (a major auction house). Not sure who to contact in the US though ... Christian
For at least the past two years Heritage has conducted the world coin auction at the Chicago International Show, and I know there is a similar auction held in conjuction with the New York International Show but I don't know if Heritage conducts that one. If you were selling here in the US I would check out those venues.