FIFA World Cup 1930 (champions - Uruguay)
The first World Cup, played entirely in Montevideo, ended with hosts Uruguay coming from 2-1 down at half-time to beat Argentina 4-2 at the Estadio Centenario - a final played with a different ball in each half by order of referee Jean Langenus because the teams could not agree, in the year of Uruguay's independence centenary.
Why this wins its question: The founding final with its two-balls anecdote bound to FIFA's own account rather than folklore retellings.
Claims
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Hosts Uruguay beat Argentina 4-2 in the first World Cup final at the Estadio Centenario in Montevideo, trailing 2-1 at half-time before goals from Pablo Dorado, Jose Pedro Cea, Victoriano Santos Iriarte and Hector Castro completed the win; all matches of the tournament were played in Montevideo.
In the absence of an official match ball both sides turned up with their own, and Belgian referee Jean Langenus ordered each half played with a different ball; Uruguay were celebrating the centenary of their independence that year, and Argentina's goals came from Carlos Peucelle and Guillermo Stabile.