1921 and on they are marked with a barrel code you can look up on the manufactured link on the Remington Society of America, before that need a serial no to tell and then only a year and not the month/year that the code provides.
Contact Remington.
Not marked, Model 9
You can call Remington Firearms at 1-800-243-9700. Listen to the prompts an it will give you a representative that can tell you the age of the gun by serial number
Check Remington Society of America here: http://remingtonsociety.com/rsa/questions/barrelcodes
No such model is listed in the Blue Book or Standard Catalog.
You cannot the serial number is required.
The model number should be on top of the barrel just ahead of the receiver the manufacture and model should be together.
Are you sure it's an auto and not a pump action, it sounds like the predecessor to the Remington Model 10.
Check this page on the Remington Society of America for a list of places: http://remingtonsociety.com/rsa/service
Date code stamp on barrel if 1921 or later, before that serial no. See related links for date code info.
You can find Remington Date of Manufacture codes at www.rimfirecentral.com in Remington Forum
Since 1921 Remington has date stamped the barrel you can find the details/table on the Remington Society of America under the Manufactured Date link.