Is interesting Mexican silver coins circulated for years in the United States and especially Texas alongside the U.S. coins. Santa Anna gave two each 8 Reals pesos or dollars to the survivors of the Alamo fight. These were dated 1834 and minted in Zacatecas. Louisiana captured a load of the 1861-O half dollars at the New Orleans mint. Nearly all the hard coins or specie disappeared and were hoarded during the war. Even postage stamps were used to make change and the small denomination private and state script.
I do not know where the Mexican specie in the Confederate Treasury came from. Perhaps cotton sales or specie deposited in various southern banks who knows.