Beautiful Pet Rock Obedience Training Certificate from the Pet Rock Supply Company printed in 1976. This historic document has an ornate border around it with the printed signatures of the Director's name W.H.O. Knows. This came along when someone purchased a Pet Rock. In 1975, small round rocks were packaged in cardboard boxes, bedded with straw. A manual was included describing how to care for the rock. Certificates were printed to be issued to the Pet Rock Owners. Selling pet Rocks was one of the classic marketing success stories up there with selling ice to Eskimos.