I read about Guinea itself, how it was made, but I don't really understand why would anybody keep a money worth 5% more than an existing denomination like Pound.
I can accept the 1/20 and 1/12 concept even though it is not as comfortable as the decimal system, but 21/20, furthermore because of the gold content the value of the coin wasn't fixed in all time, but in 1680's it's worth moved away from Pound, and it was replaced by Sovereign in the recoinage of 1816.
I don't really understand the reasons why the empire kept it for over a century?
Personally for me it looks messy without a central concept how a monetary system should be regulated within the empire. Maybe there are good reasons keeping it, but I don't see them.
To make my point more clear: I see a similar pattern in Hungary, when we introduced a .500 fine silver coin in 1993-1994 after collapsion of socialism into circulation with 200 HUF face value, shortly because of silver content it became more valuable, so people just collected them and kept it as more inflation proof money, it actually revoked itself from circulation and it was officially revoked by the government too. This was a clear failure of issue a different based money, and both people and government corrected the mistake naturally, why didn't this happen in British Empire for over 100 years? I can say the value distortion was smaller between Silver and Gold price than Silver and fiat money. But this system in the British empire seems deliberately kept up for some reason.