I find it interesting that a Charlemagne Franc at 3.75g is roughly equal to a Venetian Ducat and to a Florin at 3.5g.
In the Middle East and much of Africa, a gold Dinar or Mithqal was 4.25g. In other words, the gold units for Europe, Africa, and the ME were roughly equal.
Meanwhile in South Asia, the Tola was 11.6g or one third of a franc. While in East Asia, the Chinese Tael was 37.5g or ten times the franc.
Funny I read something to the effect that some people in Rome got paid a few pounds of gold a year which is about what people get paid today.
Just a few lines in, and I can tell this should be complementary with Debt: The First 5,000 years by the late David Graeber. Much of the book is about deconstructing modern myths of how economies used to work and how they evolved over time.