OK - that's enough to go on. wide open they cover about 30 degrees or 1/2 focal length, increasing to 60 degrees, 1.15 focal lengths, at f:22 and down. So my guess is that it was made for "Postkartengrösse", 10x15cm, and not 13x18cm. Or maybe for portraits on 9x12cm (or Kabinettkarte?).