OK - this was clear in mind until I ran across log books for a plane (1990 era Mooney) I am looking at. TSMOH is listed in the sales ad but I am having a difficult time correlating this to the logs. I see TT as a higher number than Tach but lower than Hobbs. Reading up about this, it seems this is less definitive than I thought. What should the TSMOH hours be based on? Thx.