King started operation in 1887 and was eventually owned by Daisy air gun company. Daisy kept the king name on several models. When WWII started, Daisy dropped the King name in 1942. Unfortunately there are so many models of "King" that the exact information for the 500 model is lost somewhere in history. However Daisy has a service to answer questions about old Daisy products. See the attached Link.
http://www.daisy.com/contactus
Like $500 I guess
It's rated at 500 FPS.
the most fps in a gun is 500 or more and my best gun is a mp44 because its 517 fps and it hurts and it feels like a bb gun
If you want to build your own air gun I suggest you search" You tube" and look for "Home made air guns'
The gun was made by SKB in Japan and imported by Ithaca, starting in 1966. I don't know when your particular gun was made.
Both Daisy and Crosman air guns made BB guns for Sears. you will have to state the model to get an estimate of the value. Check the model number on the gun, any model that begins with 126 was made by Crosman air gun and any model that begins with 799 was made by Daisy air gun.
Colt makes a 1911-A1 Pellet gun made by Umarex. I know of no BB gun unless you are asking about an Air Soft gun. The Pellet gun is very good. I can not answer about an Air soft gun.
It MUST be made specifically for an air gun.
What do you mean 500 feet used in gun safety?
see the link below
You mean Air Rifle. Yes this is fine. Air rifles (Not AirSoft) usually fire between 500 FPS and 1200 FPS
100-500 or so