“Four pearls at each corner of the badge represent the bases, and a line of blue enamel, running from pearl to pearl, makes a very pretty base path.” (Description of badges given to members of the Louisville baseball team) “The Ball Field: Louisville Presents Her Favorites with Handsome Badges,” St. Louis Globe-Democrat, April 25, 1876, p8
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1904. “[Dundon] has shown himself a great second baseman and speedy on the basepaths.” (W.A. Phelon, Sporting Life, Sept. 24; Peter Morris).