Sorry Demo, I did not intend to cross swords, your collection would give you greater access to on hand referencing.
Maybe that is our problem, it's easy to see fault or see nothing from thousands of miles away, you can't beat having the item in your hot hands.

I am beginning to lean more towards your post#29, I notice under magnification the remnants of buttmarks more consistant with it's age, also it appears that the buttplate overlaps the timber, showing that the butt was heavily sanded in this area.

Just to answer Detroits query regarding the MA51, this is just the barrel manufacture date, it is sheer coincidence that the barrel is the same year as the FTR, it could have been any year new barrel on hand at the time, thanks for allowing us to pick your rifle to pieces, it gives us something to do and rattles the rust from our brains.