I have my father's very finely sporterized RIA s/n 344453 which may have been built in 1919. The ramp front sight covers any barrel marking.
A second RIA I own in a scant stock is s/n 151357 built in 1908 fitted with a 1942 SA barrel.
A third Remington 03-A3 just bought at CMP Anniston is s/n 3846198 built in 1942 also fitted with a SA 42 barrel.
Thanks for any information.