Waterford city has at least 22 post boxes, many of them dating from the days when we were part of the British Empire. Some of the post boxes have ER on them and date from Edward 7th. Some even date from the reign of Queen Victoria.
Many of them are marked on the 25 inch OS map completed in 1913. Some are listed on the National inventory of architectural heritage but others are not.
I propose the post box on Parnell street which is close to the Viking Triangle (Grid reference) S 608 122 which dates from Queen Victoria. It is not listed. I have designed a route using an orienteering map and MapRun phone app. to highlight the post boxes around the city.