How would you perfect a security interest in precious metals and gold coins?

A Pledge Agreement and take possession?

Possessory would be the only way that I would do it.

P.S. Make sure they are what you think they are - it might be fake.

I was just discussing that with my co-worker. It seems that this could be the tricky part. I would think that the borrower and a bank rep would have to be together at the appraisal (which would be prior to closing) and the bank would then have to take immediate possession. Otherwise, how do we know that what we are taking at closing is the authentic collateral that was appraised.