What a great find this one was, I spend everyday in The Rocks and I didn't even know this street existed.
A friend posted some photo of Sydney on her Face book page and I saw it in the background, so next day I went and saw for myself. Not sure if in use as there was no signage on it but slots were open.
This post box has been given a new paint job in recent months as it was looking very neglected before. This one is located on the corner of Argyle and Kent St Millers Point. The wall in lives in was once a post office.