Depends on how old the revolver is.
ctg = cartridge
No difference. CTG is the abbreviation for cartridge. A revolver marked 38 Special CTG, or .38 S&W Special CTG is simply indicating that it is chambered for a .38 Special cartridge. This IS different from .38 S&W, and older, shorter, fatter, less powerful cartridge.
A K frame revolver
Any modern ammo will do, except for +P.
The term ".38 Special CTG" is an abbreviated way of saying .38 Special Cartridge. It is the caliber marking for a revolver that fires that cartridge. While it is NOW the most common .38 caliber cartridge, there are more than a dozen DIFFERENT .38 revolver catridges that were made at one time.
50-500 usd
2k What is this value based on
38 S&W ammo. which is a shorter version of the 38 special cartridge.
careful examination of barrel, butt, crane, receiver.
You will have to call S&W to find out.
Ballparking around $250-300 probably.