Not all visual Bongard Problems whose examples all have some amount of black in them are sorted left. In left-sorted BPs, there must be some concrete percentage of black that is exceeded by every sorted example.
Adjacent-numbered pages: BP1161 BP1162 BP1163 BP1164 BP1165  *  BP1167 BP1168 BP1169 BP1170 BP1171
meta (see left/right), links
Leo Crabbe