But can a country run two currencies?

Sure.  

There are problems of so doing, most notably expressed in Gresham's Law:

when government compulsorily overvalues one money and undervalues another, the undervalued money will leave the country or disappear from circulation into hoards, while the overvalued money will flood into circulation

Universally mis-quoted and mis-understood by Neo-Classical, Austrian, and other economic ignorati as "bad money drives out good money."  

[Note the moralizing in the latter, wrong, formulation!]

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre