King George's Letterbox
Introduction
The photograph on this page of King George's Letterbox by Bob Harvey as part of the Geograph project.
The Geograph project started in 2005 with the aim of publishing, organising and preserving representative images for every square kilometre of Great Britain, Ireland and the Isle of Man.
There are currently over 7.5m images from over 14,400 individuals and you can help contribute to the project by visiting https://www.geograph.org.uk

Image: © Bob Harvey Taken: 23 Feb 2019
This wallbox has a cypher for GR, but does not tell us which one. That almost certainly means it dates back to George V, according to a Geograph forum topic on the subject. So it probably predates 1936.