Martin 00-21 12 string conversion 1957 natural excellent with original case

This is a really cool and interesting guitar. It is a 1957 Martin 00-21 acoustic that was professionally converted to a 12 string. It appears that it has the original 00-21 neck but an extension of the head stock was done to accommodate the longer neck and convert it to a 12 string guitar. The work is extremely well done and clearly done by an experienced luthier. I would guess it may have been done at the Martin factory but I have no proof of that . Beautiful Brazilian rosewood sides and back. Original tortoise shell pick guard. The guitar shows very minor nicks and scratches but is overall in excellent condition. It plays very well and sounds brighter than the usual Dreadnaught 12 strings as you would expect. It comes with that appears to be the original 00-21 case in very good original condition. Pretty sure you would be the only one on your block with one of these.