Identification
A reel with a readable legend and a known construction can be placed. A reel of unknown cable cannot be installed by anyone who has to sign off on it, so it is recovery material regardless of how good the copper is.
Length
A construction with 900 feet left serves a real job; the same construction with 45 feet serves a repair. Both are surplus. Below the point where anyone can use it, the reel is metal.
Condition of the insulation
Sealed ends, intact jacket, no sun cracking, no kinks. Insulation is the part that cannot be inspected from outside, which is why a disclosure about moisture or damage changes the classification immediately.
Documentation and release
Cable that cannot be lawfully sold is not surplus, whatever its condition. Utility and government material needs a release before the commercial question even starts.