Actually... This is most likely a Model 12 made in early 1915, may not say model 12 on it and doesn't not have date code. I'm guessing if he didn't say model it's because it's not stamped on the side ;)
Please check the link for the Manufacture Date codes details on the Remington Society of America.
Need to check the barrel date code. Remington Society of America, Manufacture date link has all the details.
Remington Works - 1914 (late)
It's date stamped, check the manufacture date page on the Remington Society of America for details.
A link to the manufacture date tables by serial can be found on the Remington Society of America on this page. http://www.remingtonsociety.com/rsa/questions/barrelcodes 1942
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.