Reading through my mx logbooks, I've found several cases where an annual inspection was signed off as a 100-hour inspection.  Some of these were from before I owned the aircraft. From my read of 91.409, an annual can substitute for a 100-hour, but a 100-hour cannot substitute for an annual unless it is specifically noted in the log as an "annual" inspection. The aircraft has never been used in any commercial operation, so there is no scenario where it would have needed a 100-hour inspe