IMO, these coins came from a chest of coins. I have found stacks similar on the East Coast of Florida in an area knows as the "Spring of Whitby" site. All that were found were stacks of eight reales, which looked very similar to these. Also, keep this in mind. If the ship was lost during a storm, then many of the artifacts could actually be coming from the dunes. When the east coast of Florida suffers a big storm, we have actually found artifacts and coins on the edge of the cut at the dunes line (up in the top section of the dunes). Yes, it is possible that these were washed ashore durning a storm, BUT, if the storm that brought these items to light was strong enough to cut into the dunes, then they may have come from there as well. Remember, if a hurricane sunk the ship, it might be similar to the Florida east coast and have washed parts of the actual ship up onto the beach. Then, the dunes would have built up over the years to cover up the ships remains. When a big storm hits the same place at the correct angle, it can start exposing the long-lost items.
The coins were stacked into chests, and over time, parts can break off, leaving small stacks of coins seperated from the main source.