Nope your machine is not a 99. 99's are stubbier than the 15's. Yours is probably a 15-91 (I'm no expert) Check out this website:
http://www.sandman-collectibles.com/...r-machines.htm . There will be step by step instructions to identify your specific machine. You definitely have a 15 but which model of 15 is the question. They are great machines--I have 2!