"[W]e followed the history in general of the Letter Receivers of NSW 1856 to 1890’s. The earliest Letter Receivers in NSW were made locally by Bubb & Sons Victoria Foundry from 1856 to 1867.
The locations of those found in 2011 have been recorded. From the 1970’s they have gradually been reducing in number, many going as scrap."
https://www.flickr.com/photos/royalaustralianhistoricalsociety/albums/72157638536627233/