Villages did not need the volume of a pillar box so smaller letter boxes built into walls first appeared in 1857, with a great many variations in detail with differing designs introduced following operational experience. Wall boxes with distinctive enamel plates were made for sub-post offices between 1885 and 1965 and many of these survive. They are known as Ludlow boxes after their Birmingham manufacturer.
The final design is the lamp box, so-called as they were generally attached to lamp posts. They first appeared in 1896 as public gas lighting was being introduced and it is interesting that whilst their origin was in urban areas, nowadays they are found mostly on telegraph poles in the countryside or even built into rural walls.
The vast majority of letter boxes are made of cast iron, however plastic letter boxes are a recent innovation for indoor locations such as supermarkets, although one doubts they will survive 150 years.
Just when you thought there was quite enough variation, one should add that when a new Sovereign comes to the throne, the new Royal Cipher is used on any new letter boxes, although pre-existing boxes remain in service. A quick calculation shows that we have had six monarchs since letter boxes were introduced, so that if you wanted to see examples of them all, you would be looking for 24 types. Then there are the changes in design, so those with a well ordered disposition could be looking for examples of three or even four times that number!
We are fortunate in having a selection of wall and lamp boxes on display in the Curtis Museum and you will be amazed at the variation when you start looking at examples in local villages.