The comedian, who died in 2021, ran a farm and a contracting business from his base at Lewdown, near Okehampton, Devon.
He always used the number plate on his personal vehicle and it was even on the Toyota Land Cruiser that carried his coffin to his funeral at Truro Cathedral in 2022.
The viewing day for the dispersal sale of vehicles, farm equipment and other machinery attracted a large number of people but it was the number plate that drew the most interest.
Speaking before the sale, Harvey Pile from Stags Auctioneers said: "It is one of those iconic pieces where, to some extent, it's worth whatever somebody is willing to pay for it.
"It is a cliche thing to say but how do you value a piece of comedic history that in years to come will always be linked to the famous man?"
Jethro, whose real name was Geoffrey Rowe, was born in St Buryan, Cornwall.
His popularity as a comedian grew during the 1980s and he made his first national appearance on the Des O'Connor show in 1990.
He later said that performance gave him a national profile and it led to other TV appearances and stage shows across the UK.
In 2001, he appeared on the Royal Variety Show and went on to become one of the biggest stars from Cornwall.
Jethro had stopped touring in 2020 after more than 50 years on the road - he died in December 2021 at the age of 73 after contracting Covid-19.
His funeral at Truro Cathedral in January 2022 was attended by hundreds of people, including fellow comedian and close friend Jim Davidson.
