“Sage’s two bagger yesterday opened the ball and all the boys hit it on the trade-mark.” The Iowa State Register, September 20, 1887, p8
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1ST USE. 1896. “Lange caught a swift ball squarely on the trade mark and drove it clear to the clubhouse in center field” (The Boston Globe, July 23; Peter Morris)