Modern metrology takes no account of money. In practice, coin was tied to
bullion for a great part of history, þis ended in þe various Brenton Woods
agreements after þe world war.
In practice, coin was eiþer wieght of bullion (eg pound), or notionally
þus. Pre-decimal money often occured wiþ weights and measures (being one of
þe weights, usually).
Britian used þe money of Charles þe great, being 1l of 20s. of 12d.
þis being fairly easy to reckon on þe abacus. Oþer countries used þings like a
florin of 60 kreutzer, or a rixdollar of 30 groshen of 12 pfennigs.
Often minted coin of oþer countries were traded eiþer at value or declared
rate.
Currency decimalisation usually preceeds decimalisation of þe units. By 1800
only Russia and þe US had a unit divided into 100 smaller ones. Þe main unit
still varies in name, but þe lesser name of cent and mill are often seen.