I was in my early teens and many awkward years away from joining a gym when I found Gilbert III in the soon-to-be sticky pages of a furtively-purchased issue of John Grimek’s Muscular Development (purchased, I told the saleslady, for a fictitious older brother who asked me to pick up a copy of the magazine for him).
Many, but not all, issues featured Gilbert’s freaky, fantastic, fabulous men flaunting their bodacious tatas, wasp-waists, monster asses and thunder thighs in posing trunks or tights.
The bodies he portrayed were unfeasible, unrealistic, and unobtainable: no amount of lifting or squatting – or drugs or plastic surgery– could ever make anyone look like this. Without exception, they were ridiculously proportioned, impracticably built, and impossibly big.
Changing tastes lead to a decline in artwork like this in bodybuilding magazines. To many – especially younger men– the images look old fashioned and out of date; something from another time. Technology also meant magazines publishers had access to more graphic options. New tools allowed publishers to create the sophisticated visual content readers craved. Color photography became the norm. By the late 70s his black and white artwork had disappeared from the magazine racks.
Today you can occasionally find his men in old issues of Muscular Development in second hand book stores or thrift shops; these images were scanned from back issues purchased in an old book shop:
Sarge's Locker 
Thanks so much for posting these erotic drawings of Gilbert III. I’ve been searching high and low for them, I remember seeing them in Muscular Development Magazines.
I had a very similar experience in college in the early 1970s of furtively buying Muscular Development magazines, which were in the back of a health foods store along with Strength and Health magazine. I was amazed that such a conservative magazine would print anything as over-the-top as the Gilbert illustrations. And now, 50 years later, I find that Gilbert also did major bondage artwork, with his wildly muscled guys bound up in chains. Amazing! Thanks for describing how artwork in the bodybuilding mags evolved over the decades. Too bad that Gilbert’s work has become so obscure and hidden. Not surprising I guess, but still too bad.