Enlarging upon what Mickdude2 said...
What about monarchs being able to establish standard currency? The most basic form historically has been precious items or substance of some sort. In Europe and Asia this has often been precious metal. Monarchs put their imprints on standard-sized pieces of precious metal for two reasons: one to advertise the power of the monarch, the other to assert that the enforcement power of the monarch was behind the claim to the genuineness, hence value, of the substance in the coin.
Monarchs were able to get away with this because they were usually major purchasers of goods and services in their realms, and often the single major purchaser of such. If someone didn't want to accept the monarch's word via his imprinted substances, they would lose out on business, and might also attract unwanted negative attention from the monarch or his minions. People with personal stashes of precious substance that they had more trust in held onto it, and paid their own bills with the monarch's currency. This is a case of the adage "bad money drives good money out of circulation", where the monarch's "bad" money drives the "good" bullion (for example) out of circulation and eventually becomes the "good" money, as long as the monarchy is successful and the economy does not tank.
Paper currency originally started as a way to represent precious metal, or other substance, without having to carry it around. Bank notes were issued by banks as a promise-to-pay, but were worthless without people's trust in the issuing banks. Governments were capable of forcing people to accept paper currency when they had power, as in the case of the monarch's coins above, but when governments lost power, the paper currency became worthless, as in the case of CSA dollars.
Coinage actually made of substance that people regard as valuable will generally retain considerable value in the event of political collapse, whereas debased coinage or paper currency will not. In the former case, the recognized value of the underlying substance will be accepted in barter even if the issuing agent no longer exists. In the latter case, much or all of the value lies in the authority of the issuing agent, and will disappear accordingly should the issuing agent lose authority.