I have what I think is a J 45. I got the guitar in 1962. My wife had the instrument fully restored in1992 by a luthier recommended by Gibson. This luthier was puzzled about the model because he could not find a serial number but measurements and turners, etc. indicated a sunburst SJ 45.
Recently a certified Martin repair luthier got excited about the guitar and suggested some tune up work which is underway. He was also puzzled by the lack of a serial number and the inlays on the fret board. These inlay are diagonal and indicative of later models.
Research online is difficult but one YouTube video showed a SJ 45 with similar inlay but did not clearly indicate a date of manufacture but implied a date before 1950.
I have pictures on my iPad but cannot find a method for attaching it to this message.
Any help in identifying this guitar would be greatly appreciated.