sentences:  Kosc was the first base umpire for Len Barker's perfect game on May 15, 1981, and was behind the plate for Mike Witt's perfect game on September 30, 1984; he is one of only seven umpires to have worked in two perfect games.He was an umpire on September 6, 1995 when Cal Ripken Jr. broke Lou Gehrig's consecutive games played streak.He was also one of the umpires for the single-game playoff to decide the AL West title in 1995 and later on was one of those 22 umpires who submitted their resignations as part of a failed union strategy in 1999, a move which backfired badly for most of them, when Major League Baseball opted to accept the resignations.