As far as the Paypal business is concerned: It includes all countries that are NOT on their "worldwide page".

Several months ago Paypal (in their characteristic way) went in very heavy handed and it even suspended accounts of people selling "boots with "Cuban" style heels, etc., etc. and as nicegreensocks points out the accounts of people buying & selling collectables.

I spoke to a UK Paypal rep at the time. He reassured me, that items like stamps & postcards were excluded from these regulations. Since then I have sold several items from Paypal's list of "banned countries" - typically a keyword gets picked up, they put the transaction on hold and it then clears anywhere between a few minutes and a few hours later.

They over-reacted at the time. You are not allowed to deal with any people/organizations from those countries and you are not allowed to sell modern/new goods from those countries. However, stamps, postcards, books, old coins/notes etc are allowed.

As far as coins/banknotes is concerned - there are a number of countries that do not allow the import of "money", be it vintage (collectable) or current currency, but as I don't deal in them, I can't tell you which ones they are.