I wonder if that's ones from both East and West Berlin. The ones from the East were sourer.pH ranges for BW beers range from about 3.3 to 3.8 (as of the late 1970s; source: VLB Berlin). Most Belgian sours are between 3 and 3.6 (according to Wild Brews). For comparison, the Scottish 80/- I have sitting in front of me is right around 4.5.