In 1960, the secondary air source did not exist. In fact, single-hose regulators of that time did not have a second low pressure output; therefore, it was impossible to connect two second stage regulators to the first stage body. Also, they were not so common, since two-hose regulators prevail.
Moreover, it existed the idea to have an alternative air supply for the buddy who was possibly without it.
To propose a first solution there was the American Norseman with "Buddy Tube", presented in its catalogue of 1961. It was a simple corrugated hose which exited from the rear section of the two-hose regulator, ending with a mouthpiece. When not in use, it stayed low, fixed to the tank belt so it could not overflow; however, in this position, it was immediately ready to supply air simply taking it high and pressing in the pivoting mouthpiece to address the emergency of the buddy who could have remained almost without air or whoever grabbed it for a breathing problem. It could also be used to take underwater a friend willing to try the diving feeling.