the upper right corner of the right-hand stamp is sufficient proof that it's a line perf?
Can there be comb perf when there are different horizontal and vertical perf?
1. Certainly, if there is not a dent (part perf hole) in each of the 4 corners, then it is NOT a comb, or Harrow puncture.
2. Interesting question, I very much doubt it, I cannot see differing perf puncture
guaging meeting at the corners.
Certainly never come across it in my experience.
This punch and die pair, (Grover Perforator) should ideally indicate how the
COMB perforator punctures remain constant through the perforation process.
With each press of the punch, the bed of the perforator advances 2 stamp distances.
And how the name "Comb" was arrived at.
The distance between the two punch plates, leaves imperforate paper, between the two panes of the stamp sheet.