Type 6 Perforations (Triple comb)
In addition to the single comb Type 5
perforator a triple-row comb was also used. This was known as Type 6. It perforated two complete rows and three sides of a third row with each beat of the comb-head. The machine worked through the bottom margin and the top margin of the sheet below it with resulting perforations. Extension pins were used only on the inter-pane margin section of the sheet.
Different perforator machine used. Stamps perforated while still in a continuous roll (web) immediately after printing of the stamps. Subsequently cut into double and then single pane sheets for distribution and use.