You can then open the chest, and take from it as many pence as you please, they are only copper pence, but if you would rather have silver money, you must go into the second chamber.
Source: The Tinder Box by Hans Christian Anderson
Is that boldface correct grammatically?
Why is that "pence", not "pences"?
Best Answer
Because pence is plural. It is historically a plural of penny, and is still used that way in some contexts in British English.
Specifically, it is normal when referring to value: "one penny, two pence" (though many people say "one p, two p")
It is not currently used when referring to individual coins: most people would say "there is a pile of pennies on the table", not "there is a pile of pence on the table". In that respect, the passage you quote is archaic.