Hard to tell, a proper bred captive bred animal can also be as big as an animal in the wild,
on the other hand, wild animals can be ranging in size as well.
The only thing i can think of, is that almost all WC frogs will have marks on them,
at least more then a CB one.
So checking for (healed) injuries might give you an idea about it's origin.
Letting it check for parasites etc. also gives you an insight,
WC animals tend to have more intestal worms/parasites then CB frogs.
But it is no fool-proof science, just what i noticed with my own WC animals and their offspring i got out of them.