The Walberswick sign of a ship with the date of the Coronation in 1953 was stolen from the Suffolk coastal village under mysterious circumstances in the 1980s and the culprit was never discovered.
But the sign ended up in the garden of Lea and Philip Newstead in East London after they bought it from a friend.
Restored to its rightful place: The stolen Walberswick village sign has been put back on display after being stolen 30 years ago
Mrs Newstead said: 'If we had known it had been stolen, or if we'd even known about Walberswick before, it would have gone back a long time ago.
'People had offered us money to buy the sign and we kept saying no because we'd never researched it to find out if it was real or not.'
The couple, who now live in Allhallows in Kent, were on their way to Norfolk for a holiday when they saw a road sign for Walberswick.
Good Samaritans: Lea and Philip Newstead returned the sign after buying it as a garden ornament in London in the mid 1990s unaware it had been stolen from Walberswick in Suffolk
Back home: It is believed the village sign made for the Queen's Coronation in 1953 was stolen by bikers in the 1980s
She said: 'That's what convinced us that this must be a real sign - because it was so similar, apart from the fact that our one is about 5ft tall and 5ft wide'.
They contacted the parish council on their return from holiday and offered to give the sign back to the village.
Part of the festivities: The sign has been erected opposite Walberswick Church, in Suffolk, in time for the Jubilee celebrations
Mr Newstead yesterday said: 'I must say, it's one of the best signs I have ever seen. It is as if it was meant to be, having it back on the Jubilee weekend.'
The unveiling came as Queen Elizabeth joined an armada of 1,000 vessels and more than a million cheering spectators on Sunday to celebrate her 60th year on the throne with the most dazzling display of pageantry seen on London's River Thames for 350 years.
Pealing bells greeted the start of the flotilla as the queen's gilded royal barge sailed alongside a colourful and eclectic array of boats from leisure cruisers and yachts to rowing boats, a Hawaiian war canoe and Venetian gondolas.
Organisers said 1.2 million people, many waving Union Jack flags, braved typically inclement British weather to catch a glimpse of the procession along the seven mile as riverbanks were turned in a blur of red, white and blue.
After four hours on the river, much of it spent standing to review the flotilla passing by, the 86-year-old monarch was still smiling and showing a resolute British stiff upper lip as the event concluded in driving rain with a bitter wind.
Elizabeth, her 90-year-old husband Prince Philip and the other senior royal family members even jigged in time to the strains of Rule Britannia as the last vessel carrying an orchestra and drenched singers serenaded her.
Up and down the country, millions of people attended diamond jubilee street parties in honour of the sovereign, the only British monarch after Queen Victoria to have sat on the throne for 60 years.
The London pageant was one of the main highlights of four-days of public celebration to celebrate the Queen's reign.