I recently acquired a new Model 18, one of S&W's Classics series revolvers. It is a nice addition to my previously acquired Model 19, Model 67, and Model 642. The "dash" number on my new Model 18 is "-7". Just what was the engineering change that S&W made to this version? I have information about the engineering changes associated with the -1, -2, -3, and -4 versions, but not for the -5, -6, or -7. I suspect one involved the inclusion of the key lock feature. Another may have involved using the crush fit barrel rather than the pinned barrel. Any help in understanding these most recent changes would be appreciated.