On June 26, 1999, approximately 0845 Pacific daylight time, a tailwheel equipped Piper PA-22-108, N5059Z, registered to and being operated by a private pilot, was substantially damaged, during a loss of control on landing roll at the Methow Valley State airport, Winthrop, Washington. The pilot and a second pilot-rated passenger were uninjured. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight, which was to have been operated under 14CFR91, originated from the accident airport approximately 0800, and was being conducted as a pre-purchase demonstration for the passenger. A sheriff's deputy, who responded to the accident and interviewed the pilot/owner, reported that the pilot owner had his aircraft up for sale and that a prospective buyer was test flying the aircraft. The pilot/owner further reported that the prospective buyer was landing the aircraft when it veered to the right, departed the runway and impacted a barbed wire fence. The deputy reported that skid marks on the runway and tire marks in the gravel along the runway's right edge, as well as damage to the fence were consistent with the pilot/owner's description of events. The deputy also interviewed a witness who reported observing the aircraft touch down on all three wheels simultaneously, veer off the right side of the runway, and tip up on its right side. The pilot-in-command (owner), who was occupying the left seat, reported that he had a total of 131 hours in make/model out of a total of 196 hours. He also reported that he and the prospective buyer departed on a "trial flight for [the] possible sale of [the] aircraft" and that after some non pattern work he took the controls from the prospective buyer, entered the pattern, and accomplished two touch-and-go landings. During the rollout on the second landing the aircraft was turned over to the prospective buyer who then executed a takeoff and approach to runway 31. The pilot/owner reported that "after being on the ground approx{imately] 75-100 feet, estimated ground speed [of] approx[imately] 45-55 mph, he lost directional control [and] the aircraft veered off the right side of [the] runway and hit a fence line." The owner reported the winds as light and variable and also reported that there was no mechanical malfunction with the aircraft. Winds at Omak 25 nautical miles east were also reported at 4 knots and variable. The pilot/passenger (prospective buyer), who had no flight experience in the make/model of aircraft but indicated more than 66 hours of tailwheel experience, reported the following: "after [a] short local flight, [the] pilot returned to land, [the] first attempt was aborted, [the] second attempt was rough and [a] go around was executed. The third attempt resulted in a ground loop. The aircraft exited the runway environment to the right and impacted a barbed wire fence, resulting in a nose over. Pilot and passenger exited the aircraft and pushed the aircraft back to the hangar."