tps.org.au

I have got this cover at Australia 2013.
It shows a 1d and 2d on ship post cover to Carlton, Melbourne. Cancelled at arrival with killer 1. It is a quite early usage of Sideface issue stamped at arrival in Melbourne and Carlton - Victoria on DC 20 / 70.
Do anyone know earlier usage og the Sideface issue?

A little extra plus. The One Penny has double perforation!

The Sideface stamps were officially introduced to the public on 1 November 1870.
Denominations were 1d, 2d, 4d (blue) and 10d. The Victorian backstamps on this
cover are dated 20 OC 1870. Can we suspect an error in the dates? It seems odd
that both backstamps (Melbourne and Carlton) have the month apparently wrong.

Other readers may be able to add to the story.