X denotes 1946 I believe and an 'M' group model. Surely it should have the model number following the XM ie 20-21 etc. Likewise it should be on the original engine?? Ron
'X' as a frame prefix covered 1946 and 1947...Going by your frame number and typical production figures I suspect yours is 1947...I'd have to dig deeper to definitively confirm that though...Ian