Michel special identifies 3 different protective lacquer strips:
版本 I: 1901, 5.25mm wide with a spacing of 4.5mm
Type II: 1902, 4.25mm wide with a spacing of 5.25mm
Type III: 1903, 2.25mm wide with a spacing of 7.25mm.
ANK 2021 special catalog identifies the 1901 (type I) 和 1903 (type III) versions of lacquer strips, without giving unique number and ANK does not make difference between the perforation variants.