It would be interesting to see how an independent Scotland would deal with the huge amount of 'foreign' currency in the hands of industry and individuals - one possible way would be to introduce its own currency and restrict the level of foreign currency companies and individuals could hold - in...
International credit rating is not based on currency but on the GDP and other economic factors - if it was based on currency then all the countries in the Eurozone would have the same credit rating.
It was actually 3 years after the end of the War of Independence before the dollar was introduced. The US had much the same problem as Scotland will have if the they do gain independence from the rest of the UK.
There will companies and individuals who between them will own billions of pounds...