Your remington was made in 1928.
Early 1911
First year 1909 (RW is not part of the serial - it stands for Remington works)
All I can tell you is that it was introduced in 1909 and discontinued in 1936.
Manufactured: 1913 The manufacture month and year of a Remington rifle can be determined from a letter and number code stamped near the back of the barrel on the right side. If your Model 12 is not marked 12A, 12B, 12C, 12CS, 12D, 12E, or 12F, it is a basic Model 12.
12b-4
A 12B is a Gallery Special the manual is the same for all 12's. The only place you can find a manual or reproduction is to search places like eBay I put a manual here: http://www.remingtonsociety.com/gallery/main.php?g2_itemId=3770
A 12-B is a Gallery (short only) This was made early in 1913 Value based on condition, condition, and condition, also condition, without out that's a 100 parts or beater to 2,000.
If it's not marked it's a model 12B (B is short only/Gallery model) made in 1912 the value is dependent on original condition. From a 200 beater to a 1,200 like new or more in the original box.
The LCM is 36bc^3.
6a -12b + 30 = 6 (a - 2b + 5)
24 = 48 - 12b subtract 48 from each side -24 = -12b divide both sides by -12 2 = b
36ab = 3a x 12b so is the LCM