Check the date code stamp on the left side of the barrel you can get the details and look it up on the Remington Society of America under the manufactured date link.
100-350 USD
Made by the Remigton Firearms Company.
Serial 718943w
The W ahead of the serial number indicates that your Remington 870 wingmaster was made in 1972.
Check this table for the answer: http://www.remingtonsociety.com/rsa/questions/barrelcodes
They are all still made in Illion, New York, I believe.
Do a search on barrel codes, I believe that will give you an answer
Look at the date code stamp on the barrel, see related link.
You can call Remington at 1-800-243-9700 and go thru the menu selection. One of the menu options is to request information on your Remington based off of the serial number.
Remington Society barrel code lookup: http://remingtonsociety.com/rsa/questions/barrelcodes
Go to the Remington Society of America and click the Manufactured link, it has the location and barrel codes for month/year of manufacture.
http://remingtonsociety.com/rsa/questions/barrelcodes