Check the Remington Society of America, date barrel codes and location. http://remingtonsociety.com/rsa/questions/barrelcodes
100-350 USD
Contact Remington Customer Service through their website.
http://remingtonsociety.com/rsa/questions/barrelcodes
Made by the Remigton Firearms Company.
The W ahead of the serial number indicates that your Remington 870 wingmaster was made in 1972.
They are all still made in Illion, New York, I believe.
Check this table for the answer: http://www.remingtonsociety.com/rsa/questions/barrelcodes
To determine the exact value of a Remington Wingmaster 20 gauge model 870, a few different things would need to be taken into consideration. Some of these things would be the age and condition.
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.
Look at the date code stamp on the barrel, see related link.