Google is your friend. From: 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: A= 1949 B= 1950 C= 1951 D= 1952 E= 1953 F= 1954 G= 1955 H= 1956 I= 1957 J= 1958 K= 1959 L= 1960 M= 1961 N= 1962 O= SKIPPED P=1963 Q= SKIPPED R= 1964 S= 1965 T= 1966 U= 1967 V= 1968 W= 1969 X= 1970 I believe the extended action was not released until 1957 and the tang safety was started in 1964. Hey there, you seem to be pretty smart about all this stuff. Me and my little brother recently purchased a Savage model 99 from one my my fiance's work pals. They were an old retiring couple and they were trying to get rid of a ton os stuff. He had these four guns in his closet that his deceased brother passed on to him, and those guns in turn were passed on to him from their grandfather, etc. No idea how old it goes back, but it looks OLD and it still shoots fine.
• When using Fixed Files make sure to use a Firewall which controls outgoing traffic, as some games call back to report the use of these modified files! 
• Some original games do not work when a certain application has been installed, like DAEMON Tools.
WE dont shoot it that often though because ammo is expensive. Anyhow, the serial number is 646346 and it doesnt have a letter in it.
Any idea how old or what it could be worth?
You can't always be SURE as to the date of manufacture with Model 99s, even with a serial number. A more sure way is by what is called the 'Lever Boss Code'. As an example, if the serial number is used to judge the date of manufacturer, then the examples (below) indicate that your rifle was made in 1968 as Joe (Mad Dog) said. However, to be more sure of that date, check out your Lever Boss Code ('LBC') which is a number (the inspector's number) followed by a letter indicating the year of manufacture. Note that your rifle's serial number falls near the end of 1968 in my records (below). Note the LBC. '19' is the inspector's number and 'V' stands for the year 1968.
The Serial number is E9825XX. When I called Savage customer service to find out a manufacturing date, they stated they did not hold any records on that rifle, but I should write to the following individual and pass him all the information I had about this rifle.
U= 1967: 1134xxx, 1136xxx, 11391xx V= 1968: 1165XXX(16V), 1171xxx, 1172283(19V), 1184xxx (19V) W= 1969: A009045 (Jan), A226071 (June), A279775, A296xxx, The most accurate method of determining the year of manufacture of Model 99 rifles made from 1949 to 1971 is by using what is called the 'Lever Boss Code'. Even more accurate than the rifle's serial number. Savage began stamping an inspector's number and a letter in a poorly (and very faintly) stamped oval on the lever boss (the extension on the lower, front side of the receiver in which the lever rotates) in 1949. This is what is called the Lever Boss Code. Savage continued to use Lever Boss Code numbers & letters until 1971.
The letters 'O' and 'Q' were skipped and not used in the Code series due to their similarity. The number was the inspector's number plus the letter indicating the year of manufacture. ('A' was used in 1949, 'B' in 1950, 'C' in 1951 and so forth). And so, if a rifle were made in 1968 & inspected by Inspector #12, it would have a Lever Boss Code that looked like this (inside the oval): 12 V Please look (you may need a magnifying glass) at your rifle and tell us the Lever Boss Code.
Klyuch dlya soundbooster. Strength & Honor.