The note was put on the auction site by seller Gareth Wright on October 3 – and sparked a frenzied bidding war.
The bidding now stands at an astonishing £65,000, with one day left to try and purchase the note.
Mr Wright, who lives in Twickenham, said he had withdrawn £10 from a cash machine and got back two new £5 notes.
He spent one of notes but then noticed the AK47 serial number on the other and so decided to keep hold of it remembering they were fetching hundreds of pounds online.
He told the Sun his phone ‘did not stop vibrating all night’ after he first put the note on eBay.
But he fears he may have been targeted by pranksters as the bidding jumped suddenly from £1,000 to £6,000, from £10,000 to £50,000 and £50,000 to £60,000.
eBay have insisted any bids made will go ahead.
A spokesman said: ‘Where we believe there is unhelpful bidding activity we will take an active role in monitoring the sale for the seller.’
S/O Daily Mail