On September 28, 2011, at 1715 eastern daylight time, a Mitsubishi MU-2B-25, N344KL, registered to Laurel Mountain Aviation LLC, experienced a nose landing gear collapse during landing roll out at Cobb County Airport-McCollum Field (RYY), Atlanta, Georgia. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed. The corporate flight was operated under the provisions of 14 Code of Federal Regulations Part 91. The airplane received structural damage to the airplane nose and structure aft of the primary bulkhead. The certificate airline transport rated pilot and two passengers reported no injuries. The flight originated from Huntsville International Airport-Carl T. Jones Field (HSV), Huntsville, Alabama, at 1541 central daylight time. The pilot stated that after departing HSV, he climbed to his cruise altitude of 11,000 feet mean sea level. Upon arrival in the vicinity of RYY, he was cleared for a visual approach to runway 27. He entered a right closed traffic pattern and completed all required checklist items. The airplane touched down on the runway and the nose landing gear collapsed. The airplane came to rest upright on the runway. Examination of the airplane nose strut down lock installation revealed the strut, part number (PN) 010A-39117-11, that was installed on the right side of the nose landing gear trunnion, was installed incorrectly. The bearing "stake marks" should have been on the outboard side of the 010A-39117 strut. Incorrect installation of the strut could result in the bearing pulling loose from the pin on the right side of the trunnion. A review of maintenance records revealed recent maintenance activity on the nose gear involving the strut. The design of the strut is typical for the left and right. Both struts have the base PN 010A-39117, permanently marked by cast numbers on the outboard side of the strut. According to the manufacturer, the part should display the PN 010A- 39117-12 for the right and -11 for the left. The manufacturer issued MU-2 Service Bulletin (SB) No. 200B, dated June 24, 1994, to address the orientation and adjustment. The MU-2 Maintenance Manual did not address the installation or correct orientation of the strut. Service Bulletin 200B states on page 8 of 10 that the “Part Number may be visible in this (the) area from the out board sides (Inked P/N may be faded out)”. The accident strut only exhibited the base number. The left strut was installed in accordance with the SB. The last annual and 200-hour inspection was conducted on July 11, 2011, 10 hours before the accident. The airplane was flown to a repair station for additional maintenance prior to the accident. The airplane had a previous nose landing gear failure and had been repaired by the pilot's mechanic. A mechanic at the repair station looked at the nose landing gear down lock and observed it only had a 2 millimeter clearance. The mechanic called the pilot and informed him the airplane did not have enough down lock engagement. The pilot informed the mechanic to fix the problem. The mechanic installed a short block PN 010A-39108-125 to get the proper engagement as outlined in the maintenance manual. A review of the logbooks revealed no determination could be made as to who had previously worked on the drag strut.