Italian and German Frame Sizes
I just moved to Zurich from California and have been browsing some of the online market places here for a new road-style commute/errand bike. I've noticed that a lot of people describe frames in both Italian and German sizing, i.e., 56 Ital/57.5 Deutsch. The German size seems to be pretty consistently 1.5 cm larger than the Italian one.
Does anyone know what these measurements represent and which corresponds to the "American" size I'm used to that measures from the BB to the top of the seat tube?