Can I sell my Clipper card?

I'm curious, can someone tell me if it's possible to sell my Clipper card? I've heard that these cards can hold a certain amount of value, especially if they're loaded with unused funds or have special discounts attached. But I'm not entirely sure if there's a market for them or if there are any restrictions on transferring ownership. Could someone clarify the situation for me? I'd appreciate any information you can provide.