The usual cancel on a handback was the type H-1, no numeral time code, but a dash between the 1840 and 1890. Cards are known posted with the "P" type obliterations on all three dates.
The card below is a bit of a puzzle. By 10 PM on the night of the 16th, the entire stock of the special Guildhall Postcard was announced as 'sold out'. Yet here is the Guildhall card, favor canceled on the 19th. While the scan seems to show a blue tone to the cancel, it is really a light grey, possibly from a drying ink pad.