How long is a piece of string?
As with any saleable item that can be imagined, your card is worth only as much as someone else is willing to pay for it. You may be able to glean an asking price from one of the many eBay sellers that maintain a 'Store'. If you find such a specialized item, there may be a note on the selling page about the number that have sold at that price. Beyond that, selling your item will be at chance: what you ask has to be matched by the chance occurrence of someone who wants the item, and is willing to buy, or to bargain with you.
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