What do you do with a red post box?
Paint it blue!
One of the conditions of release of a redundent post box used to be that if it were displayed in a publicly accessible place, it must either be painted a different colour or blocked up if kept red.
So when the Trinity Street box in Halstead was damaged in 1999 and donated to the Museum, it had to be blue! Not just any old blue, but Guernsey Post Office blue. There are two boxes of this type on Guernsey (PB42/1) and so it was an authentic choice, enhanced by a real collection plate kindly donated by Guernsey Post.
This picture nicely shows the various parts of a pillar box. There are three basic castings - the door (which now includes the aperture), the cap (in this case fitted with a bracket to hold the Post Office Direction sign) and the carcass - which is the rest of the box, cast in one piece.