J.C. Higgins Model number shotgun, normally 20-12
The JC Higgins Model 20 58359 is a shotgun that was produced by the J.C. Higgins brand, which was associated with Sears, Roebuck and Company. This particular model was made during the 1950s to early 1960s. To determine its exact age, you would typically look for the date code on the firearm, but in general, it can be considered to be around 60 to 70 years old as of 2023.
That is not a serial number (that gun does not have one) it is a model number. Your shotgun is a High Standard Flite King- good guns, by the way. They sell used for about $130
"Shotgun" means the passenger side.
I am guessing you have a model 870. It is a edition of the 870 shotgun
This is a double barrel, over/under shotgun.
If you call out shotgun it means you get the front passanger seat in the vehicle.
The number 1400 refers to the Model number of your Winchester shotgun.
a shotgun
Unknown.
Improved cylinder
Go here for a good explanation - http://hunting.about.com/od/shotgun/l/aastshotgunfaqa.htm
Degree of choke