There are two brands of 85/15 string that I know of. The D'Addario "American Bronze," which is what you saw, and the GHS Vintage Bronze.

These strings are useful if you have a guitar that has a sound that is too "bright" or "brassy" for your taste when played with PBs or 80/20s, and you want a "darker" or "smokier" sound.

Sorry I can't be more clear about the distinction. Who was it said that "Writing about music is like dancing about architecture?"

Peter.