1909 to 1936 with a serial can date it, also 1921 and later are date code stamped on the barrel.
1914
Early 1920.
1919
1920
Late 1911
1927, check related links for date code on barrel look-up month/year.
1924, see related links
Your Remington model 12c is going for anywhere from 400 dollars in 60% condition to 800 dollars for one in 90% condition.
1923, see related link it's date coded.
1911
Bottom of receiver in front of trigger
Manufactured 1914