These are cups used for beverage sales at the Old Met Stadium. The dealer's listing dated these as 1956, which is when Met Stadium opened and the Minneapolis Millers played there. But these cups say "Major-League Baseball Stadium" and the Twins didn't play there until the 1961 season.
So I'm not convinced of the date, but it's late 50's or 60's.
I'm not sure why I decided I needed to have these, but I thought they were pretty cool.