What was the key currency (money) used in the Middle Ages

one way people would buy items in the middle ages is by bartering

Explanation:

This is exchanging an item/items for goods and services.

This was a commonly used method of trade in that time period

on november 6 and 7, 1917 (or october 24 and 25 on the julian calendar, which is why the event is often referred to as the october revolution), leftist revolutionaries led by bolshevik party leader vladimir lenin launched a nearly bloodless coup d'état against the duma's provisional government.