My Stevens center fire rifle has serial number G378943, also has A1202 on barrel. What do these numbers mean?

this is copied from a site, the web address is pasted below.

The serial number depending on the model of rifle, will be located either on the upper or lower stock tang, or side of the receiver.
http://www.gunvaluesboard.com/marlin-serial-numbers-dates-of-manufacture-1664.html

also if you find serial # you may find more info here.
http://oldguns.net/sn_php/marlinlookup.php

From 1962 thru 1968 Marlins rimfire rifles (other than the 39 series lever actions) used a two letter date code that was stamped on the barrel. This date code is different than the one already listed, as Marlin rimfire rifles (other than the model 39 series) did not have a serial numbers until required to by Law after 1968. The first letter of the date code represented the month of manufacture while the second letter indicated the year. This date code was usually stamped on the left side of the barrel just in front of the receiver.

According to this website (http://www.gundigest.com/gun-collecting-firearm-collecting/sqa-stevens-letter-prefix-serial-numbers) it sounds like it would be between 1913 and 1939.

Look at the date code on the left rear part of the barrel. Google 'Remington Date code' to intepret.

Look at the date code on the left rear portion of the barrel. The codes are posted on line.

It would help if you told us shotgun or rifle, center fire or rim fire, pump, falling block, lever, bolt action, or auto loading, etc.
Then it would help to simply see what fits into the end of the barrel.
Next would be to measure the length of the action.
After 1921 Remington use letter codes for year and month, so this would have to be earlier than that, since it has no letters.