Interesting thread, as a "non-techy" I immediately thought you were referring to counter-rotation as provided on the Fairey Gannet, an aircraft with which I was extremely taken in my "yoof"!
First seen at RAF Nicosia about 1956, wondered how they could go different ways off the same shaft, my knowledge of mechanics being rather rudimentary!
Eventually found that power was provided by twin Armstrong Siddeley Mamba turbines and separate gearing and shafts.
The US came up with something similar in the Douglas Skyshark which, unlike the Gannet, only had the one Allison engine.