I sold such a gun about a year ago ( 6/05 ) for six hundred and fifty dollars. It was a "red letter" in about eighty percent condition of original finish with a repaired stock. The person who bought it back bored it for "turkey shooting". Go figure!!
"Your" Winchester Model 21 Double Barrel Shotgun was manufactured in 1933, giving it an age of 77 years, as of 2010.
The model will be stamped on the barrel right after the Winchester name.
Look on bottom of receiver and barrel
It was made in 1937.
10-500 usd
The Winchester 140 12 gauge has a choke barrel at 28". This is the same choke size as the 20 gauge model.
A Winchester 12 gauge model 1200 pump shotgun holds 2 in the tube and 1 in the barrel. So it holds 2+1 which makes 3 total.
Impossible to answer.
Depending on condition 300-1000 USD.
Your winchester model 12 shotgun was made by winchester in 1953.
Your winchester model 12 shotgun was made by winchester in 1937.
Your Winchester model 1897 shotgun was made by Winchester in 1910.