On August 7, 1995, about 1500 eastern daylight time, a Cessna 152, N67597, registered to and operated by Seven Eagles, Inc., was substantially damaged during a forced landing near Spring Hill, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 personal flight. The private-rated pilot, the sole occupant, was not injured. The flight originated about 1430, from the Tampa Bay Executive Airport, Odessa, Florida. The pilot stated that after departure he flew to a nearby airport and performed four touch-and-go landings then circled another airport. While returning to the departure airport during cruise flight at 1,200 feet, the engine rpm decreased. He immediately initiated a descent and landed in a pasture. During the landing roll the airplane nosed over. The airplane was recovered and the engine which remained secured to the airframe, was started. According to a FAA certificated A & P mechanic, the engine failed when operating only on the right magneto. The right magneto was removed for examination which revealed that the condenser lead was failed at the condenser. Review of the engine logbook revealed that the magneto which had been overhauled was installed on the engine on August 23, 1988.