On October 7, 2003, at 1120 eastern daylight time, a Cessna 210L, N59063, registered to and operated by the United States Customs Service, made a forced landing into a field following a loss of engine power near Tallahassee, Florida. The flight was operated as a Public Use airplane under the provisions of Title 14 CFR Part 91, and instrument flight rules. Visual meteorological conditions prevailed and an IFR flight plan was filed. The pilot and pilot rated passenger were not injured and the airplane sustained substantial damage. The flight originated from Jacksonville, Florida, on October 7, 2003, at 0800. According to the pilot, while in cruise flight at 10,000 feet agl, the engine lost power. The pilot made a wheels up forced landing into a field. Examination of the undercarriage of the airplane found structural damage to the skin, stringers and frame components. Examination of the engine found a large hole in the outer case. The engine was crated and sent to Teledyne Continental Motors (TCM) for further examination. Maintenance history indicated that the engine had a propeller strike on February 19, 2003. The engine was removed from the airplane and sent to Certified Engines Unlimited, in Opa-Locka, Florida for inspection. The engine had a total time since major overhaul (TTSMOH) of 509.2 hours. On March 21, 2003, the engine was reinstalled on the airplane and returned to service. On May 13, 2003, the engine was removed and sent to Certified Engines Unlimited, due to a crankshaft counterweight failure TTSMOH 535.1 hours. The counterweights were replaced and the engine was reinstalled on the airplane June 12, 2003. On October 7, 2003 while in cruise flight the airplane had a catastrophic engine failure TTSMOH 734.1 hours. On April 26, 2004, the engine was examined at TCM. Present during the examination were representatives from TCM, NTSB, and the US Costume Service, Department of Home Land Security. The engine was completely disassembled and examined. Examination found the crankshaft fractured through the number one connecting rod journal forward fillet radius and upper counterweight hanger blade. The number three connecting rod journal was fractured at the rear fillet radius. The number four connecting rod journal was fractured at the forward fillet radius. The crankshaft was distorted along its length. The number one and two main bearing journals had scoring. The remaining connecting rod journals, main journals and thrust surfaces were undamaged and showed no signs of abnormal wear or lubrication distress. The rear upper crankshaft counterweight was detached from its hanger blade. One plate and snap-ring was forced from their locations on each side of the counterweight by mechanical action of the pins. The counterweight plates of this counterweight were bowed outward in relationship to there installed positions. One of the snap-rings was fractured in two pieces and both snap-rings that were not in place exhibited signatures of being forced from their retaining grooves in the counterweight. The remaining rear counterweight exhibited sever mechanical damage and was intact on the hanger blade. The forward set of counterweights, pins, plates and snap-rings were intact and undamaged and had free and unrestricted movement on the hanger blades. The crankshaft gear teeth were severely damaged as a result of the through fracture.