“99” or “ninety-nine” (manager)

Newspapers.com
9 February 1930, Tampa (FL) Sunday Tribune, “Soda Jerkers Here Talk in Language Hard to Understand,” pt. 4, pg. 6, col. 2:
99—Here’s the manager.
 
Newspapers.com
29 March 1936, Helena (MT) Daily Independent, “National Youth Administration Compiles Lexicon of the Soda Jerker After Five Months Work” by Helen Dallas, pg. 2, col. 8:
“Ninety-eight” is the manager, “ninety-nine” is the head soda man, and a “pop boy” is a soda man who does not know his business.
 
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27 September 1981, The Herald Statesman (Yonkers, NY), “Counterwailing” by Dan Carlinsky, Suburdia Today, pg. 18, col. 4:
99. The manager.
 
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10 July 1985, The Times-Mail (Bedford, IN), “Soda jerk unique on American scene” by Ink Mendelsohn, pg. 5, col. 5:
NINETY-NINE—head soda man
 
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29 November 1997, Pueblo (CO) Chieftain, “Word Mysteries” by Chris Woodka, pg. 5A, col. 4:
99—The boss. The assistant manager was 98.