A good while back, there was a ton of mid-grade stuff coming down from Canada. Most people called it "beasters." It wasn't bad compared to a lot of the brick sold in the states, but you could tell it was mass produced. Most of it turned out to be M-39. I guess it is (or used to be) a good strain for commercial production. Good calyx to leaf ratio and high yields, but probably not the best for overall quality, just good for commercial purposes.
It was the catalog number for sssc (super sativa seed club) Strains were labeled: m-1, m-2, m-3, etc. It was a Northern light#5/ skunk#1 but they couldn't name it that because of copyright from sensi seed bank. Quick finisher, very easy to grow, no odor and a very indica buzz wich you quickly get fed of. I suggest to stay away from this.