You might try the date system on Remington's web site here... http://www.remingtonsociety.com/questions/BLACKPOWDERX.htm ....and possibly find your answer.
June, 1941
March 1940
Check date code on barrel, see related links
June, 1948
check the date code stamped on the barrel. Remington Society of America, Manufactured Date link has the details.
The serial number of Remington rifles will not give you the date of manufacture. The two or three letter code stamped on the base of the barrel will tell the year and usually also the month of manufacture. On a Remington 121 this letter code OS usually on the left side of the barrel right next to the front of the action. I have a 121 with the letter code "OF". This indicates that my gun was made in July of 1937.
When was the serial? They all have serials. They were made from 1936-54 and have date code stamps on the barrel which can be looked up on the manufacture date link on the Remington Society of America.
1951 but if you want a more accurate month/year it's date code stamped on the barrel, location diagram and codes on Remington Society of America.
Has to have more then a K needs at least 2 letters... I would guess it's KE for May of 1936.
Check the date code on the barrel. See related links for information on the Remington Society of America.
Check the date code stamp in related links.
Check date code on barrel - see related links