“55” or “Fifty-five” (root beer)

 
 
Newspapers.com
10 July 1985, The Times-Mail (Bedford, IN), “Soda jerk unique on American scene” by Ink Mendelsohn, pg. 5, col. 4:
FIFTY-FIVE—root beer

Newspapers.com
29 November 1997, Pueblo (CO) Chieftain, “Word Mysteries” by Chris Woodka, pg. 5A, col. 4:
55—Root beer.