SPx: In 1996 Upper Deck introduced a new super-premium product called SPx. Billed as "SP to the X degree," SPx was marketed as a base set with "insert quality" cards, and sold in one-card packs for $2.99. Although the set was met with initial success, the lack of rookies, and overproduction eventually doomed it.
In 1998 UD reintroduced the brand as "SPx Finite." As the name suggests, Upper Deck created a product in which every single card (base set, parallel and insert alike) would come out of the pack serial numbered. The second series of '98 SPx Finite is significant as it was one of the first baseball products to have serial numbered rookie cards.
The 1999 and 2000 SPx sets eschewed the "serial number everything" approach, but still featured a subset of numbered prospects. However, as with most Upper Deck products of the era, hardly any of them are "true rookies."
In 2001, Upper Deck upped the ante by including game-jersey and autographed game-jersey rookie cards (all were numbered as part of the base set), including an autographed gamer of Ichiro Suzuki.