Breakfast is not the time that I find myself totally awake so I had to look twice to be certain.
From The Wall Street Journal [click images for larger view]:
I'm never going to get used to this new accounting. When I took Latin back in high school [many decades ago], one million was written as MM and one thousand was written as M. Must be the effects of inflation since then. A horizontal line above the M can be used as an alternative to MM for one thousand.