At the post Second World War Bretton Woods conference Keynes proposed an interational reserve currency, the Bancor. It would be regulated by an International Clearing Union, like the International Monetary Fund during the Bretton Woods era. It was desinged to encourage equal terms of trade between nations and to prevent another great depression. In OTL the United States shot the idea down as they prefered to have the USD as the world's reserve currency.
So what would the effect be if this proposal had been adopted?
More info:
wikipedia
I'm not at all sure this would be a good idea or even work.
With the US Dollar (or British pound, or whatever) if you want to buy goods from the US (or Britain, or whatever) you just buy them, if you have the reserves. If you don't have reserves, then you can't buy anything.
I'm not sure that government controlled institutionalized bartering, which is what this sounds like, would lead to any sort of efficient market at all. I suspect that people are going to end up using national currencies (mostly the US Dollar) anyway.
Worst case scenario, it could end up a disaster worse than the Euro currently is. (Note: I don't think the Euro's a bad idea, it's just that the deficit mechanisms that were to make it work were totally ignored by GERMANY, of all countries, and so why should Greece or Italy pay attention to them. Oops.)