Remington traced its heritage to Eliphalet Remington, an early American gunsmith who produced his first flintlock rifle in 1816. Raised in Central New York, Remington purchased land along the Erie Canal in 1828 and established an armory.
Remington does not do factory letters.The Remington Society of America maybe able to help you at least date your firearm but most early records were lost in a fire and only some of the early percussion information was able to be pulled from military records and other very early firearms only can be dated by model and variation. (estimate)
Remington Arms Co., Inc. Remington, once owned by a Delaware holding company, DuPont Chemical and Energy Operations, Inc., was sold to Raci Holding in the early 2000s.
It's described on the Remington Society of America forums... http://remingtonsociety.com/forums/