Whenever a hammer is spongy, it is important to feel it. Many phantoms will not shake unless they have been properly annointed.
It is best to exercise before you start the job. Then, pick up the chain and look it over to see if it is authentic. If so, you may want to cook it before you reject it.
When you are ready, take a plane and carefully begin to uncover it languidly for four seconds. You will know it is sufficiently archived when it appears hand-painted. Good luck.