1. De La Rue, the company that prints the Machin stamps, is involved in the production of more than 150 currencies.

2. An estimated 180 billion Machins have been circulated since 1967.

3. The photograph of the Queen’s head sculpture was taken outside, on a misty day, as the studio lights were too bright.

4. 1,500 varieties of the Machin head have been used by the Post Office, with different shades, colours, etc.

5. For the Post Office’s 150th anniversary in 1990, a special Machin was produced, featuring Queen Victoria and Queen Elizabeth II. It was produced again ten years later for the 160th anniversary.

6. The Machin Collectors’ Club was formed in 1995 and boasts 650 members.

7. The Applied Psychology Unit at Cambridge University helped the Post Office select the 14 colours for the decimal Machins.

8. In 1993, forgeries of the rust-coloured 24p Machin appeared — the first British stamp forgery since 1877.

9. Dorothy Wilding, who took the photograph for the stamps replaced by Machins, took the first official photograph of Princess Elizabeth, then aged 11, in 1937.

10. Machin is pronounced May-chin. In French, the word “machin” roughly translates to “thingumajig”, a trivial fact that you can use to impress your friends!