When I was 17 and wanting to get into bodybuilding, I became friends with Mr. America Rich Baretta. He in turn, set me up with Bob Gruskin. Yes the same Bob Gruskin who was Arnold's guru. He helped me prep for a couple of shows until I decided the amount of drugs that were in higher level bodybuilding wasn't for me and I switched to power lifting.
We spoke in depth about old time bodybuilding etc. and he once told me that similarly to how we use Equipoise now from horses, the Germans use gorilla hormones to gain muscle and that this was what Arnold, Louie, Franco etc. were all on. This is a 100% true story that this is what he told me...
And D-Bol was huge back then. They took a lot of it.
How true HIS story was about gorilla hormones, I have no idea. Take it as you will.