PEOPLE are only just realising what the colour of their post box means after a rare shade was spotted by baffled residents.
Only two post boxes painted the special colour can be found in the UK, with thousands of locals passing them every day without noticing.
The sky-blue post box, signifying special air mail postal service, can only be found outside Windsor Castle and on Liverpool Road in Manchester.
Several red post boxes were also painted royal blue in 2019 to celebrate England hosting the Cricket World Cup.
Others were given a mid-blue colour to thank NHS workers during the first Covid-19 lockdown.
Bearing the monogram of George VI, the sky-blue post box in Manchester was originally red - but was repainted in 1983 to commemorate the opening of the city's Aerospace Museum.
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A commemorative plate on its rear reads: "This box is painted blue to represent the special 'air mail' boxes erected in Great Britain between 1930-38.
"It commemorates not only the long association of the Post Office with British aviation but also our support for the Manchester Aerospace Museum."
Post box expert Robert Cole told the Manchester Evening News: "The Manchester one is one of the better known ones.
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"It’s a really, really lovely piece of post box history. You can imagine things about who posted things through them and what sort of life they had.
"The post office set up letter boxes in 1862 but in the 1920s this exciting thing came around called an aeroplane.
"They were able to charge more for air mail, so it was an opportunity really.
"They put up special boxes and had special vans that were sky blue and a huge advertising campaign from that time."
The Postal Museum's Corinne Galloway added: "By the end of the 1930s, there was a change in the way that mail was processed.
"It became more work to have a separate function. They announced the end of the blue post boxes in 1938 and they went out in 1939.
"That’s where they are quite rare. There were only ever 300 and most were removed or repainted red."
People are also only just realising what the GR and ER symbols printed on post boxes really mean.
Brits were left "mind-boggled" after finding out what the bottom of post boxes really looks like.
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