An agreement in principle to sign the-then-13-year-old Messi was written on the napkin almost 25 years ago at a Barcelona tennis club. A more formal and detailed contract with the club followed soon after.

An undisclosed percentage of the sale price pays administrative fees for the online auction, in what's called the buyer's premium.

Bonhams said the auction was on behalf of Horacio Gaggioli, an agent from Messi's home country of Argentina who was part of the deal.

The contract language, written in blue ink, was intended to reassure the teenager's father, Jorge Messi, that the deal would go through.

Jorge Messi had threatened to take his son back to Argentina because negotiations with Barcelona had stalled.

The napkin, containing the date December 14, 2000, bears the signatures of Gaggioli, another agent, Josep Maria Minguella and Barcelona's then-sporting director, Carles Rexach, who met at a tennis club.

Rexach had asked a waiter for paper and was given a blank napkin.

The starting price was 300,000 pounds (USD 379,000).

Messi spent nearly two decades with Barcelona after arriving from Argentina at 13 to play in its youth squads. He made his first-team debut in 2004 and played 17 seasons with the main squad. He helped the club win every major trophy including the Champions League four times and the Spanish league 10 times.

Messi left Barcelona for Paris Saint-Germain in the summer of 2021. He has since joined Inter Miami.