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I'm not sure I understand your question of "Original"... The RW stands for Remington Works", a name used at the time for the Remington factory. According to the serial #, your M/12 was made in 1920, the year before date codes were added by Remington.
If you are looking for additional reference material, Roy Marcot's and my book Remington .22 rimfire rifles has 23 pages on the M/12. Ordering instructions are under books on this site. I believe foreign shipping is approximately $25.