Some sheets of this issue has missing perforation in one direction on parts of the sheet.
The vertically perforated sheets seem to
a/ have horizontal perforation between rows 2-3, (3-4?), 4-5, 5-6. 
b/ have only the top/bottom of the sheet imperforated (50B + 1L)

The horizontally perforated sheets seems to have at least 2 variations as witnessed by the 2L
and the 10L shown here.

Perforated in one direction + partial perforation in 2 directions
  var1.jpg (10554 bytes)
  Var2.jpg (11160 bytes)
  Sw3-2.jpg (16599 bytes)
BB21-6.jpg (16224 bytes)BB21-4.jpg (15836 bytes) BB21-1.jpg (9145 bytes)BB21-2.jpg (11724 bytes)BB21-3.jpg (8307 bytes)
BB27-1.jpg (30522 bytes)  
1926-6L.jpg (12819 bytes)  
  Sw4-2.jpg (18257 bytes)
bbking.jpg (8509 bytes)

BB27-2.jpg (15236 bytes)
missing and misplaced perforation