The Memory stamp is a piece of technology used by the People of P3R-118.
The technology removes most memories from an individual, superimposing a new identity over the real memory. It appears to be less effective on humans from other worlds, including the Tau'ri, whose original memories soon resurface and replace the implanted memories. The technology is even less effective on Jaffa, whose suppressed memories will resurface within days of a stamp, and the use on Jaffa is impractical from the beginning due to the Jaffa's need to Kelno'reem meaning that a more effective stamp would cause them to forget what they needed to do to keep themselves alive. (SG1: "Beneath the Surface")