I would guess this hand-painted poster was not made to advertise the Powder magazine that covered skiing and snowboarding, but rather a more grassroots publication which I have to think contained some pretty explosive content! Feels very much late 1960s or early 70s to me, and definitely executed with an immediacy that suggest it was hung right above a stack hot off the press. 

14 1/2" x 11 1/4" with a center fold line and a few light creases and a couple of tears coming in from the edges. Oh, and with a pencil drawing of a pirate on the back!