Hi. This is my first post so I hope I dont screw it up. Tried to attach pix but it seems I need to post 10 times first. My question is I need some assistance in interpreting my serial number. It is 640FMWE89072. Specifically what dioes the letter M stand for? The top tube calipers to about 28.9cm, but I'm assuming it is Columbus SL/SP tubing due to the 640 size. Any help is appreciated. (9 posts to go and then I'll post pix). Thanks