On an unknown date, time and location, a Cessna 172M, N4395R, registered to and operated by Hill Flying Club, was substantially damaged during an unknown flight operation. The weather is unknown at the time of the accident, and it is unknown if a flight plan was filed. The pilot, and if passengers were on board at the time is unknown. It is presumed that there were no injuries. On July 1, 1997, a flying club official reported to the National Transportation Safety Board, Northwest Regional Office, that during annual inspection, the mechanic found that the firewall was structurally damaged. The last annual was performed in June of 1996. The official stated that he does not know when, where, or who damaged the aircraft. There are approximately 60 members in the flying club. July 1, 1997, is listed in this report as the accident date for computer entry purposes only.