your pistol was made by colt in 1918. you are probably reading 'remibgton rand' off the slide. It is not unusual to have the wrong slide on a colt pistol. this happends when a number of 45's are broken down for cleaning and parts are mixed when put together.
1920
That is not a serial no of a Remington 1911A1 they stopped in 1945 with 2465139.
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
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