gold, page-106008

Firstly, gold was used by central banks as a reserve up until 1971. Secondly, up until that point I could walk into any bank in the USA and convert cash into gold. Not sure where your 200 year figure was plucked from!
I do agree that smart people don't keep their money in cash but you would have to be a special kind of dumb to buy 10 year bonds considering the real rate of return is sitting at negative 5.5%.