The Signature Series was a program where an artist would design a model, and then the Stone Co employees painted them. Each model had a stylized sticker of the artists' signature, and came with a Certificate of Ownership.
Metheringham Upton Isaac is a light dapple grey Trotting Drafter. This model was a prototype and painted, and signed, by Karen Gerhardt. All models came with tack. This model was made in 2001 for the regular run, but signed later by Peter in 2003.