On September 18, 1999, about 1600 Eastern Daylight Time, a Cessna 182, N2001G, was substantially damaged while landing at Pepperell Airport (26MA), Pepperell, Massachusetts. The certificated commercial pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local commercial flight conducted under 14 CFR Part 91. The pilot stated that he returned to 26MA after carrying skydivers. He landed on Runway 24, and the nose gear collapsed. The airplane went off the left side of the runway, onto the grass. During the landing, the nose gear, cowling area, and both wings were substantially damaged. According to the pilot, and a Federal Aviation Administration Inspector, four bolts secured the nose gear assembly. Two of the bolts were missing, and rust was evident in the slots where the bolts were originally secured. The pilot searched the runway area, and found one of the bolts. The bolt was forwarded to the Safety Board Materials Laboratory for further examination. Examination revealed that shearing was evident, consistent with a secondary failure. The other bolt was never recovered. The pilot stated that he believed a bolt failed, causing a failure of the nose landing gear. He added that the bolts had never been replaced during the 9 years he owned the airplane. He did not know if they had ever been replaced prior to his purchase of the airplane.