[XorNot]

Proving you're not getting duped with plated lead is actually pretty hard to do without high technology, hence the reason gold coinage came into existence and then gold depositories and banking and all the rest.

Gold is transitorily convenient provided you exercise military force over a domain - that is you can force gold to be accepted for debts within your dominion. Nothing about it makes it intrinsically valuable otherwise - and more importantly you having gold doesn't grant you wealth because you didn't economically contribute to the system to start with.

Turning up with all the gold you want would get it rejected or siezed because it wasn't an approved coinage.