Carolus (coin) explained

Carolus is the name given to a number of gold coins:

• a coin struck during the reign of Charles I of England. It was originally valued at 20 shillings, but later 23.
• the Carolusgulden first minted by Charles V (Holy Roman Empire) in 1517, see Dutch Guilder#History
• the Carolus dollar, a Spanish-American peso or piece of eight issued by Charles III (1759-88) and Charles IV (1788-1808) of Spain.^[1]

References

1. "Carolus". Oxford English Dictionary. Oxford University Press. 2nd edition. 1989.