Kind of a whim piece; this is the Rattler, a member of the Serpent Society. I love my Serpents, and I'm a fan of the original Marvel Handbooks. I'm not as big a fan of the 1990s "Master Edition" versions, which tended to be all facts and no context, but this page was affordable (in 2012 terms) and very fun to see. Far from a grail piece, but still cool.
     The three views seen here are intended as artists references - in a pre-internet era (before you could just Google up some images of a character), an artist could have the set of these at home and get all the details he needed to draw the characters based on these front, side, and back views. That said, the Rattler's tail here is way wrong, and not representative of how its been drawn before or since. While your average snake's tail does reduce down to a point as pictured here, a rattlesnake has a thick rattle at the end, as does the Rattler's costume. As a general rule, the Rattler's tail does not shrink, or if it does then it certainly does so to a much lesser degree, and it should have a largish rattle at the end. I also think this is also thinner than his tail usual appears (for comparison, look for him fourth from the left in my pin-up from Captain America Annual 10). Normally I'd consider that all to be too nitpicky to even note as a comment, but as I just said, this is intended as an artists' model. I'm kind of surprised that it slipped past like this.
     Also a minor note - written in blue pencil (and so not photocopiable and thus intended for the artist only) at the lower right is a small note reading "Body Type 'B'".
     A number of Society members were pictured in the Master Edition, and one collector has managed to grab a good chunk of them. If you'd like to see others, you can find his collection at his page at the Comic Art Fans website. He also has a few more Serpent Society non-Handbook pages.
     I purchased this in May, 2012, from kochcomicart.com.