Remington Firearms are dated not by serial number, but by a 2 or 3 LETTER code stamped on the barrel, left side, just forward of the reciever. The website for the Remington Collector's Society has a table that deciphers the letters into month and year. Pretty accurate for rifles, may not be as accurate for shotguns (their barrels are changed easily)
There is also a partial factory record book I put online on the site on the same page and some members of the society that have serial lists from 1905-1931 for many models.
You can call Remington Firearms at 1-800-243-9700. Listen to the prompts an it will give you a representative that can tell you the age of the gun by serial number
1920
Remington firearms are dated by using a 2 or 3 LETTER code stamped on the barrels, not by a serial number. This is a link to the Remington Collector's website showing the letters and their location on the barrel. Good luck! https://www.remingtonsociety.org/manufacture-dates/
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