1) Incommutable 2) Unconvertible 3) Untransmutable 1) Irredeemable 2) Not interchangeable 3) Unconvertible 4) Unexchangeable 5) Used especially of currencies 
• (a.) Not convertible; not capable of being transmuted, changed into, or exchanged for, something else; as, one metal is inconvertible into another; bank notes are sometimes inconvertible into specie.
In`con·vert'i·ble adjective [ Latin inconvertibilis : confer French inconvertible . See In- not, and Convertible .] Not convertible; not capable of being transmuted, changed into, or exchanged for, something else; as, one metal is inconvertible into another; bank no...
[adj] - used especially of currencies 2. [adj] - not capable of being changed into something else
unconvertible adjective used especially of currencies; incapable of being exchanged for or replaced by another currency of equal value
(of paper money) not capable of being converted into specie. · not interchangeable.