In 1968 the Gun Control Act, [aka: the GCA of 1968], was passed in the US. Part of the GCA of 1968 required that newly manufactured firearms be stamped/inscribed with a serial number by the manufacturer, and located on the receiver or frame. Firearms made before 1968 were not required to have a serial number and therefore most, [especially house brand and utility grade weapons], lack one, or if present might be found anywhere on the weapon. Now firearms made under contract for a military or government organization, etc. will almost definitely bear a serial number as most militaries & government agencies require one for records purposes, to keep track of who has what.
For further info on the 1968 GCA: http://www.atf.gov/pub/fire-explo_pub/gca.htm
try: SAVAGE SHOTGUN.COM
If your rifle is a lever action?Then it is a model 99 savage and with the serial number you provided it was made by savage arms company in 1921.
You will have to contact savage arms directly to get the answer to your question.
You should contact Savage arms directly,they should identify the year of manufacture for your rifle.
Contact Savage Customer Service through their website.
What is your serial number?
I can say that the Savage model 775 was made from 1950-1965.You may want to try Savage Arms companys home page and see if you can get a certain year of production by your serial number.
Your savage model 1899 rifle was made by the savage arms company in 1901 with the serial number 15779 that you provided.
Your Savage model 99E was made from 1960-1982 by Savage arms company.As to the exact year of production,you will have to contact Savage directly.
I would contact Savage arms directly.They should be able to help you age your rifle.