Pedigree Query

I'm posting this one for a friend --

When Penn Nat'l held a public auction a month or so ago, I picked up a dozen American Racing Manuals from the late 70s to the early 90s.

A friend asked me to look up her horse's record, so the 1990 book says he raced in 1989 as follows:

A Sex S 1 2 3 Won
3 C 1 M 0 0 0


Her question -- what does the "M" mean?

Thanks for anyone who can help!

Maiden. He had not won a race yet.

That was my guess, but she deserved better than that --

Thanks, Austique!