One of one
A one of one is a card made in a single copy, usually serial numbered 1/1. It is the smallest print run a card can have, and its price depends mostly on the player and the product.
Also called One-of-one.
In more detail
Makers mark most one of ones with a serial number reading 1/1, so the card itself states that no second copy exists. A 2009 beginner's glossary on Upper Deck's site notes that their prices range widely, since the player and the product decide most of the price.
Some cards are one of a kind by nature. A logo patch card holds a team or league logo patch from a jersey, and the same 2009 glossary counts these among the one of ones. Printing plates, the plates used to print a card and then cut to card size, come in black, cyan, magenta and yellow, and each plate is a single piece.
Check the stamp against the listing. Most one of ones carry a 1/1 number on the card, and a parallel numbered to 5 or 10 is scarce but is not a one of one.
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