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 - and the attendance handled the same way: a precise figure for this match is quoted to the unit almost everywhere, and FIFA's own account of it carries no such number, only a capacity crowd of over 60,000. What is published here is what the source says, not what the retellings agree on.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
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.
FIFA's account of the match states no precise attendance for the final: it describes the hosts as "cheered on by a capacity crowd of over 60,000 at the newly built Estadio Centenario". No figure to the unit appears anywhere in it.