The Wealth of Nations by Part 4 Chapter 3 Page 13

In some it is more, in others it is less worn, clipt, and otherwise degenerated from that standard. But the value of the current coin of every country, compared with that of any other country, is in proportion not to the quantity of pure silver which it ought to contain, but to that which it actually does contain. Before the reformation of the silver coin in King William’s time, exchange between England and Holland, computed in the usual manner according to the standard of their respective mints, was five-and-twenty per cent against England. But the value of the current coin of England, as we learn from Mr. Lowndes, was at that time rather more than five-and-twenty per cent below its standard value. The real exchange, therefore, may even at that time have been in favour of England, notwithstanding the computed exchange was so much against it; a