This was the standard pillar box design in the 1870s, and the first to be manufactured in red. However, it was expensive to produce so was replaced by a plainer, round model. About 150 Penfolds survive, but they are so popular that the Post Office have recently supplied about 100 replicas to various locations.
Readers of a certain age will recognize the name Penfold. Dangermouse's hamster sidekick was named after these boxes!