I wonder - how is it possible to have perforation similar to 11:11:11:11 1/2 (like Germany BIZO Mi#99IYP - see below) and not to have perforation 11:11 1/2: 11:11? I guess for each stamp 99IYP we should have neighbor in the sheet (to the left from 99IYP) with perforation 11:11 1/2:11:11.
