On the 700's they started going up the alphabet every 5 years starting in 1970 (or 80 - eek) I just don't remember HOWEVER all 700's are date code stamped ;)
On the left side of the barrel just before receiver with month/year. The details of this/table are on the Remington Society of America, I will add a related link with pointer to information.
1920
I checked www.oldguns.net and they show the manufacture date of Remington 1903A3 serial no. 3851292 as 1942.
RW isn't part of the serial no, it stands for Remington Works 1915
That is not a serial no of a Remington 1911A1 they stopped in 1945 with 2465139.
1914
1913
1920
1919
late 1919
1920
1915
1912