i don't actually see the answer to edit but there is not "significance" in the serial or meaning it's just a serial. There's a prefix on the model 700's starting in later half of the 70's do to the date code rolling over but other then that Remington doesn't put an meanings in them.
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.
They are all still made in Illion, New York, I believe.
Check this table for the answer: http://www.remingtonsociety.com/rsa/questions/barrelcodes
Look at the date code stamp on the barrel, see related link.
Do a search on barrel codes, I believe that will give you an answer
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.
See related link.