On March 20, 2001, at 1737 hours Pacific standard time, a Beech C35, N7MK, struck a taxiway sign on the landing roll on runway 24 at the Fullerton Municipal Airport, Fullerton, California. The airplane was operated by the owner under the provisions of 14 CFR Part 91 as an instructional flight, and sustained substantial damage. The owner/private pilot and a certified flight instructor (CFI) were not injured. Visual meteorological conditions prevailed for the local area flight. No flight plan had been filed. The flight departed the El Monte, California, airport at 1720, with a planned stop in Fullerton, and back to home base at the Whiteman, California, airport. The pilot provided a written statement to an inspector from the Federal Aviation Administration (FAA) Van Nuys, California, Flight Standards District Office (FSDO). He stated that he contacted Fullerton tower and received clearance to land on runway 24. He conducted the prelanding checklist, including the GUMP check. On short final his flight instructor verified that the airplane was configured for landing. The CFI visually verified that the landing gear was in the down and locked position by checking the mirrors located on the tip tanks, and that the green light for the landing gear was illuminated. After touchdown, the pilot noted a 5-knot crosswind from the left and applied left aileron to correct for it. The pilot reported that the airplane veered off the runway to the right, and he heard the right wing hit something. Both pilots believed that the right main landing gear had started to collapse. At that point the CFI took the controls, advancing the throttle to abort the landing. The pilot stated that after the CFI established a "safe" rate of climb, he contacted the tower to let them know that they were all right. Both pilot's then started checking the airplane's systems to determine what happened. The pilot stated that they requested a long downwind to conduct emergency gear extension procedures. As they turned onto final, they requested that Fullerton tower visually check the landing gear. As they flew by the tower, personnel in the tower indicated that the landing gear appeared to be down. The pilot reported that they requested a low approach and a right crosswind departure for Whiteman airport. Fullerton tower approved their request. No further anomalies were noted during the flight to Whiteman airport. No difficulties were encountered during the landing at Whiteman airport. After landing they were given permission to taxi to parking. Once the airplane was secured in the owner's hangar, he and the CFI telephoned Fullerton tower and gave a report of what happened. Subsequent investigation disclosed that the aircraft contacted and damaged a runway edge turnoff sign. The incident was upgraded to an accident on April 12, 2001, after the Van Nuys FSDO determined verification of damage to the right wing on March 22, 2001. An FAA inspector interviewed the pilot/owner. The owner stated on the landing rollout the right wing seemed to dip and the CFI took over and initiated an aborted landing. He further indicated that he was not sure of how or which controls were manipulated after the aborted landing. The FAA inspector reported that the CFI might have inadvertently selected the landing gear up instead of retracting the flaps as he had intended. Another FAA inspector further stated that the right main tire and inner sidewall of the tire were cut circumferentially. He indicated that ground contact while the gear was in transit could have caused the tire wall to come into contact with the gear door. The landing gear was subsequently electrically tested with no mechanical anomalies noted. ADDITIONAL INFORMATION Review of the aircraft logbook revealed that on October 5, 2000, an annual inspection was completed. The airframe and power plant mechanic who inspected the airplane verbally communicated with the owner, as well as providing a squawk sheet, that parts 91.411 and 91.413 were due. No further discrepancies were noted