What unique achievement in the history of professional baseball did Ron Necciai do in 1952?

On May 13, 1952, playing in the Class D Appalachian League in the Pittsburgh Pirates' farm system, Necciai stuck out 27 batters in a 9-inning no-hitter, the only pitcher ever to strike out that many in a nine-inning professional game. Four runners reached base against him: one each on a walk, an error (one of the two batters to put the ball in play against him), a hit batsman, and a third-strike passed ball (which enabled Necciai to get four strikeouts in one inning, making up for the one batter who grounded out to first in the 4th inning). Thus, 26 of the 27 outs recorded by Necciai in his complete game were strikeouts. By the way:

In his next start, Necciai threw a 24-strikeout two-hitter.

https://en.wikipedia.org/wiki/Ron_Necciai