6 June 1941 - This Day In History

New York Giants use plastic batting helmets

The idea of making helmets a required part of Major League Baseball was discussed by officials of the National League in a meeting at the 1940 MLB All-Star Game in Chicago. Ford Frick, president of the National League, showed the helmet he designed with the hopes that the league would adopt it. Frick told the Associated Press, "[A batting helmet] is the only way I know that we can prevent head injuries and the only way we can make the players wear them is make it a league rule." Though the National League at this meeting did not adopt it, Jackie Hayes became the first player to wear the helmet in a game on August 22, 1940.
In 1941, the National League adopted the use of a helmet, designed by George Bennett, a Johns Hopkins University brain surgeon, for use by all teams in spring training. On March 8, 1941 the Brooklyn Dodgers announced that the team’s players would be wearing the helmets during regular season games. On April 26, 1941 the Washington Senators joined the Dodgers as the only two teams to fully adopt the batting helmet for regular season use. The New York Giants on June 6 and the Chicago Cubs on June 24 also joined the list of teams to fully adopt the use of protective helmets during games.

At posted coordinates find two numbers
Black on White: ABCD
White on Black: EFGH

N 32 54.(C+D)(D)(B+C) 
W 117 08.(F-1)(G-H)(E-G)

Checksums North=20, West=7 

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