I'm a bit confused, 20 British shilling was suppose to be worth one pound of sterling silver, but 66 shillings were struck from a pound of sterling silver, which meant the shilling coin itself was over-valued by more than 3 times its weight in silver. Can someone explain how this works?
Ended up finding the answer to my own question. Apparently the pound sterling itself underwent debasement more than a few times over the course of both English AND British history.
This was happening even before the shilling coin had been created, and by the reign of Elizabeth I, a pound sterling in money was actually only worth 1/3 pound weight in real silver (60 shillings struck from a pound of silver, or 3 monetary pounds for 1 pound of silver).
It gets worst after the Recoinage Act of 1816, as the shilling and other coins became a token currency, which meant the amount of precious metal in them wasn't even worth their face value.
If you go all the way back, the pound (£) hasn't been worth a pound of silver since Edward I started debasing it in 1300.