Given the amount of silver involved, I am glad that this had a happy ending and kudos to Provident sending the funds quickly. As for the USPS, that is a wildcard that you never know how that will turnout.
I agree with this because I used registered USPS mail one time since becoming an ebay seller to ship a high value (over $400) vintage Coca-Cola 1-oz silver art bar to a customer that won one of my ebay auctions. As a seller, I could not afford to let anything happen to it while in transit because that would be a big loss to me with no recourse if the package got lost or stolen. Registered USPS mail was the best protection for me as an ebay seller when shipping a high value silver art bar order to a customer.
Registered USPS mail is recommended for high value items in my opinion. It is, IMO, close to having peace of mind that the package will get there in one piece.