Serge was my all time favorite bodybuilder. I watched him guest pose in the early 90's. He was a very nice man and had what I consider to be perfect symmetry.....a true work of art.
I hate to ruin your fantasy about being natural. My boy was friends with his girlfriend, a flight attendant back in the day, who used to bring him parabolan from France and everything else they all used in the 70's, but who gives a shit really. There is nothing wrong with using anabolics. It's all about building the perfect body and he trained like an animal. He told me he did 1,000 full sit ups every morning which took him 45 minutes non-stop and he did it for 40 years at the time that I met him.