Rare unnumbered proof set of all seven 1991 Score Mickey Mantle special insert cards, each signed by Mantle in blue Sharpie. Each card has been encapsulated by PSA, with the signature certified as "Authentic." In 1991, Score became one of the first companies to include special insert cards in its regular-issue baseball packs. The subject of the special insert set was Mickey Mantle, whose career was chronicled in a series of seven cards. Approximately 36,000 of the Mantle insert cards were randomly included in Score packs. However, as a special prize, Score had Mantle sign 2,500 examples, with each card bearing a special signed limitation number. Due to their limited number, few collectors were lucky enough to obtain just one signed card, let alone a complete signed set. This extraordinary offering is a rare unnumbered proof set, which probably originates from a Score front office employee. Mantle has signed each card on the front, except for card number 1 (all card number 1s in the set were signed by Mantle on the reverse because the front was too dark and provided poor contrast for the signature). All the signatures are boldly scripted and grade 9/10 or 10/10. Near Mint condition overall. Also included is a complete unsigned set of seven cards (NR-MT).