Six players from the Amsterdam Interzonal (1964) would qualify for the Candidates quarterfinal matches in 1965. Portisch and Reshevsky had shared eighth place, but since no country, by virtue of a FIDE ruling, could advance more than three players from the Interzonal, a playoff for the sixth spot was needed. (1) This took place in Amsterdam right after the Interzonal tournament. The winner was best of four games (2) or the first to get 2,5 points.
In the absence of Robert James Fischer (who had refused to play in the Interzonal), Reshevsky, the doyen of American chess had been lured out of an 11-year boycott of the Interzonal tournaments. (3) American hopes were revived, for Reshevsky had never been beaten in match play. Then for the first time in his 44-year chess career, he lost such a match. (3)
Amsterdam, Netherlands, 25-29 June 1964
Portisch advanced to the Tal - Portisch Candidates Quarterfinal (1965).
1 2 3
1 GM Portisch 1 ½ 1 2½
2 GM Reshevsky 0 ½ 0 ½
(1) The Times, 22 June 1964, p. 9.
(2) The Times, 23 June 1964, p. 10.
(3) Larry Melvyn Evans in Sports Illustrated, 20 July 1964, p. 45.
Original collection: Game Collection: Amsterdam Interzonal Playoff 1964 by User: Tabanus. Dates are from Dutch newspapers at https://www.delpher.nl/nl/kranten/.