97 ( +1 | -1 ) Capa was clearly . . .. . . master strength by age 12 (when he won a match against Corzo, a master-level player) and probably reached GM strength sometime between then and the age of 20 when he was clearly SUPER-GM strength (crushing one of the top 10 players in the world, Marshall, 15-8 in a match and winning the year's strongest GM event).
With both Capa and Fischer and perhaps other "oldtimers" like Kasparov even, the "date" of GM is a little deceptive because they did not have opportunities to play in GM norm events earlier and then demonstrated GM skills on their FIRST TRY (!). That is, Fischer's first international event was the Interzonal, where he qualified for the Candidates Tournament as one of the top 10 players in the world and automatically became a GM, but he was clearly GM strength at 14 when he won the US Championship. Similarly, Capa won his international debut at San Sebastian ahead of Rubinstein, Nimzo, Schlecter, etc. These days, a young player usually gets many chances to play in norm events and can gain the titles more quickly as a result.