1920
I checked www.oldguns.net and they show the manufacture date of Remington 1903A3 serial no. 3851292 as 1942.
That is not a serial no of a Remington 1911A1 they stopped in 1945 with 2465139.
RW isn't part of the serial no, it stands for Remington Works 1915
1914
1913
1920
1919
late 1919
1920
1915
1912