[throwaway744678]

Looking at the source of the default configuration (cat /usr/share/misc/units.lib), I believe it only defines conversions for currencies that are pegged to another one (mainly to EUR or USD).

    You have: 10 franc
    You want: dollar
    conformability error
     1.5244902 euro
     1 usdollar
    You have: 10 franc
    You want: euro
     * 1.5244902
     / 0.655957