So the US wasn’t the only country that minted and melted millions of large silver coins that didn’t circulate
The British didn't melt them, they just overstruck them or counterstamped them in the late 18th and early 19th centuries.
Especially after the Battle of Cape Santa Maria on 5 October 1804... It would have taken years to recoin all the silver that was, seized/stolen.
Nice looking coin the OP posted and the other one posted by Ksorbo was nice as well. I own some 8 Reales coins as well, but nothing that old!