I was reading Ted Haigh's fine cocktails history/manual that came out a few years ago, what a great book, well-written and full of both historical and practical information. (The sub-cultures that exist in the mixology world certainly reveal some fascinating arcana, like the Tiki tradition of drinks on the West Coast). Haigh gives a recipe for a Cuba Libre, whose origins go back to the Spanish-American War, not later political developments including the Communist takeover. He prescribes 2 ounces rum, a half lime squeezed, and a few ounces cola, about three is right. I tried this and it is really good, my rum blends are perfect for it albeit I design them for neat drinking.
Haigh considers cola underutilized in mixology - as opposed to mixed drinks - and I would agree. There is a cola off-shoot called cola tonic which featured in a number of Jazz Age cocktails. It is not made any more in America. Apparently it is somewhat like cola syrup. Ed, if you see any in South Africa maybe you can bring one to the next Gazebo - it's still going strong there per Mr. Haigh.