Check here for anything pre 1950 http://www.savage99.com/savage99_dates.htm
but if ts after that check the lever boss code:
In 1949, Savage began stamping a tiny, lightly impressed oval on the lower, front side of the "lever boss".
The “lever boss” is the extension of the lower part of the receiver into which the lever fits and rotates. Inside the oval, Savage stamped the letter "A" together with other numbers which are apparently inspector’s numbers.
On many Model 99 rifles, this “oval” is indistinct or difficult to read as are the letters and numbers inside the oval. On my own late model “EG”, serial #709XXX, made in 1953, only the upper case letter “E” and the rear half of the oval’s circumference (which looks like a large, faint, backwards letter "C") barely show on the lever boss. The front half of the oval’s circumference and whatever is inside the oval in front of the letter “E” are indistinguishable.
The letters “O” and “Q” were skipped and not used due to their similar appearance.
Here is a complete list of the Lever Boss Codes and their corresponding year of manufacture: