The 878 was discontinued in 1962
Made from 58-63. 100-300 USD
150-175 depending on the condition and which barrel is on it
I have seen them selling for around $130, but condition would be a significant factor.
Your Remington model 1903 was made in the year 1941,with the serial number that you have provided.
It was in production from 1931 to 1949, when it was superseded by the Remington 870.
your Remington model 512 was made from 1940-1962,with a total production of 395,000 guns.
With the serial number that you have supplied,your Remington model 1903 rifle was made in the year 1941.
1930'S
1912
Check the manufactured date link on the Remington Society of America for details.
The Model 1100 has been made since 1963 and is still in Remington's catalog.