On July 31, 1999, at 1100 central daylight time (cdt), a Cessna 310N, N310DE, experienced a left main gear collapse while landing on runway 27 at the Flying Cloud Airport, Eden Prairie, Minnesota. The pilot and passenger were not injured. The airplane was substantially damaged. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The local flight originated from the Flying Cloud Airport, at 1000 cdt. The pilot reported that the flight was uneventful until the landing. He reported the airplane was lined up on the centerline of the runway in a 400 foot per minute descent during the approach. The pilot reported that the left main landing gear "broke" on touchdown. He stated the airplane "slowly drifted to the left" until the airplane came to a stop. The airplane contacted a taxiway information sign and the nose gear collapsed prior to the airplane coming to rest. Post accident inspection revealed the left main landing gear strut collapsed rearward damaging the left wing aft spar. Inspection of the left main gear revealed the upper and lower portions of the scissors link had become detached from each other allowing the lower portion of the strut to rotate within the upper portion of the strut. The bolt, washers, bushings, nut, and cotter pin remained attached to the upper link. There were three washers present near the head of the bolt. All three were painted white and had an outside diameter of 3/4 inch. There were four washer present at the castellated nut end of the bolt. None of these washers were painted and all of them had an outside diameter of 9/16 inch. This is the same outside diameter as the bushing and same inside diameter as the hole on the scissors link.