I noticed in your Economic Development Series, you propose the use of fractional reserve banking methods to generate loans. This would require the (existence and) acceptance of deposit slips (paper money) throughout the entire realm. Is there any indication that Westeros has progressed that far in Banking terms? Could this be one of Viserys’ financial reforms that he introduced, learned from his time with the Rogares in Lys? Also is Westerosi coin Bullion or “watered down” currency.?

As long as there’s a system of negotiable instruments – bills of exchange, promissory notes, letters of credit, etc. – you can basically run fractional reserve lending by giving out loans in the form of letters of credit that can be sold on by merchants to buy wool cloth or wine or ships or whatever. If negotiable instruments didn’t exist in Westeros, I don’t think most of what Littlefinger’s been up to would work, and the Iron Bank’s international banking would be incredibly complicated by the necessity to physically transport coin in bulk across the Narrow Sea. 

As for Westerosi coin – well, the Iron Throne’s currency seems to be heavier and purer than the Gardeners’ coins, suggesting a better ability to extract precious metals from across a continent and mint more valuable currency. But issuing coins in pure gold is usually a good way to lose money, so it’s probably not 100% pure. I’ve done some rough estimates about how much a golden dragon is worth here.

Replica coins that are being made seem to be around ½ a troy ounce of gold.