Four or five slight breaks, jags or dots in the West outer frame line West and South West of the bottom of the South West figure "7"; 2 or 3 small dots touching the frame lines South East of the bottom of the South East figure "7".
Kershaw's notes
Both the bottom of the LL frame lines have a scatter of dots attached.
Morel's notes
Hatches in lower left frame line, 3 guide dots on left (top, middle and bottom), 3 marks in LR frame line right of "7".
Stamps from printing orders 1 to 5A were perf. 11.75, stamps from printing orders 5B to 7 were perf. 12 x 11.75 and those from printing orders 8 to 12 were perf. 12.