inconvertible

Not redeemable for money in coin.

Not able to be legally exchanged for another currency.

Not convertible; incapable of being converted into or exchanged for something else: as, one metal is inconvertible into another; inconvertible bonds (bonds that cannot be exchanged for others of a different tenor).

Not convertible; not capable of being transmuted, changed into, or exchanged for, something else

Not convertible

not capable of being changed into something else

used especially of currencies; incapable of being exchanged for or replaced by another currency of equal value