That's an incredible find - banner for sure. However, it's my opinion that since you know what these are (a stack of 1700s spanish silver coins whose denomination can easily be determined by measuring the diameter), I would leave as is and not try to separate. I think it has much more historical value and eye appeal with the stack remaining intact. That might sound crazy, but if you can come up with a way to stabilize the coins in that configuration I would definitely not pull them apart. Again, congrats on a super find, and you definitely need to expand your search area as there could very likely be many more. Good luck!