Yep just been out to the garage torch in hand and the Frame is stamped MC18-1015504. Speedo drive is off the front sprocket cover as well. Has the frame been changed at some point?
Edit
Just looked on the parts manual on the site and it appears the numbers didnt ru in order. It Shows MC16 - 1008077 ~ 1020966 but then on the MC18 opening page is shows MC18 - 1000020 ~ .Then MC21-1000001~1024051.
It would appear that they reset the numbers almost every time a new model came out.