Here's a typical "Marvel Masterwork Pin-up" from the olden days. Marvel produced these little gems now and again, sometimes as premiums in the annuals and elsewhere, but often as page fillers for comics which ran short in some way. This one seems frankly to be the latter. It appeared in Mighty Marvel Western #46. The figures of Kid Colt, Two-Gun Kid, and Rawhide Kid all seem to be drawn by Jack Kirby and inked by Dick Ayers.
The same figures were used on the covers of Mighty Marvel Western as icons, part of the logo beginning with issue sixteen of the comics rather impressive Bronze Age run. But where did these distinctive images first appear. As it turns out all three are not surprisingly from classic Kirby and Ayers covers.
The Kid Colt figure first appeared on the cover of Kid Colt Outlaw #95 from the winter of 1960. Colt is busting out of town, guns blazing as cowboys clamber all over the somewhat off-scale buildings to get a good shot at the infamous Holstein haute-coutured owlhoot.
The Two-Gun Kid image first shows up on the cover of Two-Gun Kid #62 from 1963, imbedded in a wordless thought balloon as the damsel wishes the more heroic masked hero were on the scene to assist the atypically bold and brazen Matt Hawk. Little does she know of course.
The Rawhide Kid drawing first appeared on Rawhide Kid #20 from 1961, and showcases Mrs.Bart's leather-clad little boy facing off against his enemy in the middle of the street as the townsfolk shuffle off to seeming safety. The comment though about the Kid's ability to draw seems off point as his pistol appears already pointed at his opponent.
All comics companies are well practiced at re-purposing artwork, squeezing out the last gram of value from the hard work of their employees. It's always fun to track down these classic images in their original environments.
UPDATE: Here is a vintage 1965 ad which features the very image used in the later pin-up. The original images were apparently assembled for the first time for this merchandise. Thanks for the tip Darkmark.