I have three post apocalypse tribes who each produce different goods, let's say black beans (protein dominant), potatoes (carb dominant), and vegetable oil (fat dominant). They're unifying into a larger confederacy and want to build commodity backed notes pegged to multiple goods as a guard against volatility and against one tribe being able to dominate the control of inflation/deflation. So if, for example, disease swept through the potatoes and reduced the harvest the currency would experience a less extreme level of deflation since in vague theory it would be buffered by the normal availability of black beans or palm oil. In practice though I'm uncertain how this would work.
And that's our question: How might a multi-backed commodity currency work? To simplify things, lets assume spoilage isn't a concern (magic, some advanced tech mcguffin survived the fall etc). Are there any real world equivalents? I know that over in Massachusetts land, they've talked about pegging the value of BerkShares to a basket of local goods as way of insulating the currency from the dollar fluctuations but I haven't been able to find any hard arguments about how this would work.