1857 Penny Red on cover sent from London on May 31, 1860

The Penny Red was originally issued imperforate. Perforations, (experimental gauge 16), first came into use in 1850 and were officially adopted in 1854. In January 1855, the perforation size was changed from 16 to 14 as it was found that the sheets were coming apart too easily. The reduced size allowed the sheets to remain intact until pressure was applied to force the separation.

Each stamp has unique corner letters AA, AB, AC ... AL etc., so its position on the plate can be identified.

1857 Penny Red on cover sent from London on May 31, 1860