This. But even better, so as to prevent any surprises upon arrival, is to simply contact Customs before you leave and ask them your questions with the specifics of your situation and you can rely on their answers more than you can rely on the answers not from actual Customs officers in a discussion forum (however accurate they are).

And certain types of coins are always prohibited no matter their value.

Remember there is no limit on how much you are allowed to bring in but there are limits on how much you can bring in without being required to declare. Declaring, even if well below the limit, can always be done. Depending upon how much you are bringing, be prepared to be able to document how you legitimately obtained them. In some cases, US law enforcement authorities have broad discretion to seize assets on the spot if the officers believe the assets were not obtained legitimately. The process to get the assets returned is lengthy, arduous and usually costly.