context: Conlan umpired in the National League from 1941 to 1965, officiating in five World Series (1945 World Series, 1950 World Series, 1954 World Series, 1957 World Series and 1961 World Series) and six Major League Baseball All-Star Game (1943, 1947, 1950, 1953, 1958 and the first 1962 contest). He also umpired in the playoff series to decide the NLs regular-season champions in 1951 National League tie-breaker series, 1959 National League tie-breaker series and 1962 National League tie-breaker series (some sources erroneously credit him with umpiring in the 1946 NL playoff as well). He was the home plate umpire when Gil Hodges hit four home runs on August 31, ; he also umpired in the April 30,  game in which Willie Mays hit four home runs. He retired after the 1964 season, but returned to work as a substitute umpire for 17 games in 1965.
question: How many National League tie-breaker series did Conlan umpire after 1955?
answer: 2