This piece is either Peter's or his son's, Michael. It looks like someone took the trouble to remove the signature from the bottom perhaps to make them look older (a practice that used to be common with Casas Grande pottery). Peter and Michael almost always sign and date their work. Peter is pretty sure they are Michael's although they could be some of Peter's early work. He has been an active potter for 36 years and can't remember for sure. These would have been done since 1977 when he moved back to the reservation there.  Michael started doing pottery when he was in high school for extra money.