At the very top of any Ripken collection sits a card there is exactly one of. The 1998 Fleer Ultra Masterpiece #143P is a true one-of-one — the single Masterpiece parallel of his Ultra card, unique in all the world.

The idea was brand new then. The hobby had only invented the 1/1 a year earlier, and the notion that a card could be singular — not merely rare, but one — was still settling in. Ripken's is among the early examples of the concept that now sits at the summit of high-end collecting.

Not rare. One. The single copy that exists anywhere.

You can't really shop for a card like this. It surfaces when its owner decides to part with it and not a moment sooner, which for a one-of-one can mean years, or never. Less a card to chase than a card to know about — the apex of the Ripken pyramid, by definition unrepeatable.