M1 represents the Ranger medic course. It's equivalent to a Paramedic on the civilian side, where the SF is more towards a Physician level. The M1 is just a extra MOS indentifier. 68W= reg medic(EMT-B), 68W M1= Spec Ops Medic (EMT-P) -Ranger Medic.
Sory, I stand corrected. Should be W1...