Showing the watermark as seen on the reverse of the stamp.
Wing margins
Wing margin stamps come from the left and right stamps of each pane. Therefore 50% of this issue have wing margins. Be careful of stamps that have had their wing margin trimmed and then reperforated.
1859 Transatlantic mail. Very fine envelope sent from London to Peterboro, Canada. Prepaid at the single 6d per ½oz Canadian packet rate by a 6d Lilac (SG 68) tied by a London City "12" numeral with a red, crossed circle inspectors mark alongside and a Liverpool transit datestamp for FE.19.1859 at lower left. Letters not directed to a particular line could be sent to the first packet to sail, even when paid the correct postage for another line. Although this cover was prepaid at the Canadian Packet rate it was sent from Liverpool per Cunard steamer "Europa" to New York as this was a more expensive packet rate the cover shows a "1" accountancy handstamps for deficit due for onward delivery through the United States and a "2½cy" Canadian currency equivalent.
Wing margin stamps come from the center part of the sheet. In the pane shown above the left column of stamps have wing margins, There is no such thing as a straight edge perforated stamp in GB stamps.