A team has finished a game with 5-6-6 runs-hits-errors line 7 times since 1897, most recently ATN on 25 July 1937. That is about one every 63,286 team-games.
Box score for the most recent one ↗
5-5-4 5-5-5 5-5-6 5-5-8 5-5-7 5-6-1 5-6-6 5-6-0 5-6-2 5-6-5 5-6-3 5-6-4 5-6-7
The whole distribution — Runs-Hits-Errors Lines · All 18 shapes