HA!
While I wasn't able to find any published instance of this painting, I did come across the ALIEN, which, in my mind, is a pretty good means of at least identifying the artist:
Malcom Smith!
He did many covers for
Amazing Stories in the Forties, as well as other pulps, before going on to become the art director for
Other Worlds. He also continued to paint their covers, as can be seen with the May, 1950, issue, below. He went on to develop a style of art that combined photo prints and painting to create hyper-real fantasy and science fiction images, which supposedly look really cool (though I haven't stumbled across any covers of his which use this technique). A relatively unknown (today), but somewhat important sf artist.
After speaking to a few art and pulp experts out there, it's my guess that the painting I own is a sketch, either to rough out an idea for a possible cover, or for personal use (to give to a friend, to study composition, etc). I'm leaning towards the latter -- it just feels more likely. This would help explain how it ended up in Forrest Ackerman's collection (though it could have done so in many different ways).
I suppose it's possible that a fan artist copies Smith's alien for use in his or her own painting -- but I have my doubts. For one thing, the line work in the painting is pretty authoratative, even in so rough a sketch. It's hard to tell in the posted images, but the woman's hair is pretty finely wrought, and the layered colors, brush strokes, and overall composition speak of someone who knows what he's doing. Also, I'm pretty certain a fan would have signed the painting -- it's well done, and at least good enough to put one's name to. (Heck, I'd be proud to have painted this... but then again, I'm not a particularly good painter!) A professional artist, on the other hand, knowing that this was just a sketch -- a thumbnail of an idea -- wouldn't have bothered with a signature since it's not a "finished" piece.
Anyway, unless someone says otherwise with certainty, I'm gonna be optimistic and call this a Malcom Smith sketch. Suddenly, a weird little painting that didn't cost much at all -- but had a fun, funky, pulpy quality to it that I love -- has become a surprisingly cool treasure!
