Esiclene is around since the 70s and even then BBs went so far and injected silicone directly in their muscles...
Synthol came around in the 1990s (1996).
Not accounting other "experiments".
Well his weird shaped arms give it away.
No idea what's actually in them but there is something...
This just isn't natural:

Scott had the same bicep shape even in his early years with his brother. Wrestlers develop deformed biceps and forearms from years of pulling movements and takedown drills like both steiners, Kurt angle, mark Coleman, mark Kerr notice all same weird bicep shape.
There is a picture of scott with a cast on his left bicep after the tear in the early 90s which is the bicep he always flexed and kissed. He curled 100-120lb dumbells easily when I saw him training at Golds in 2000.
No synthol no pmma or anything else just freak genetics and hard work. You'd have to be dumb to call him a fake in whatever category of life. Guy was seriously an ideal of genetics and athleticism and IMO he'll never be matched by anyone. Not to mention he was a tough mother fucker.