Was down Florida for a couple days visiting my Dad and took the opportunity to hit the "Treasure beach's at low tide. Found a 5"spike not pictured and this Musket ball. Pretty happy with both. technically I found this past Weds.
Don't have either at the moment ... Looks to be in the 70-75 cal range roughly and you're right it is big. Im not certain bout I think smoothbores of this era were large caliber