1914
Early 1920.
Late 1911
RW is Remington Works, not part of the serial no. 1912.
Not clear if this is the question your asking but if your wondering the age of a Model 12C with serial no 178616 it was made in 1913.
1911
1923, see related link it's date coded.
1920 (pre date code) and maybe even Model 12 on the receiver?
RW isn't part of the serial it's Remington Works Made - 1910
1920
Manufactured 1914
1919