I would guess it was made by Stevens.
Laurona
I have a 16 gauge double barrel for sale.
Double barreled shotguns are manufactured in several countries.
Unknown.
Probably HD Folsom
Sold by Sears Roebuck. Probably manufactured by Stevens.
1966 to 1988
YES
Hunter Arms Company, Fulton, New York
If it is side-by-side, probably Stevens.
"Your" Winchester Model 21 Double Barrel Shotgun was manufactured in 1933, giving it an age of 77 years, as of 2010.