Please post a pic of the viewer. There are many different types and models within a manufacturer and of course, condition. Cards can be worth next to nothing for the very common types and worth $$$ depending on subject, age, local interest, photographer, etc. Civil war cards are very desirable as are early Indian cards. These would be just a couple of subjects that may bring considerably more money. You need to go through them one by one and search on the internet for an exact card. Hundreds/thousands of common cards languish in shops even at $1 per card.