Kebaya Stamp Sheet - Two Types

If you are into stamp sheet collecting, you may need to pay attention to the two types of Kebaya stamp sheets due to the perforation patterns (see images below). It looks like these perforation patterns exist in the 50s stamp sheets only, not the 30s stamp sheets.

left: the right corner is not perforated; right" the right corner is perforated

left: the right corner is not perforated; right" the right corner is perforated