Very cheap Sp at this level, page-228

420 - urban slang for weed. 840 being double strength. Best in brownies.

'As far as anyone can tell, the phrase started with a bunch of high school students. Back in 1971, a group of kids at San Rafael High School in San Rafael, California, got in the habit of meeting at 4:20 to smoke after school. When they’d see each other in the hallways during the day, their shorthand was “420 Louis,” meaning, “Let’s meet at the Louis Pasteur statue at 4:20 to smoke.”
Somehow, the phrase caught on—and when the Grateful Dead eventually picked it up, "420" spread through the greater community like wildfire. What began as a silly code passed between classes is now a worldwide event for smokers and legalization activists everywhere—not a bad accomplishment for a bunch of high school stoners.'