How about using a column like identifiers? Unfortunately, there does not seem to be a Custom Column like identifiers, but that does not stop you from using it.
The only issue, is redownloading metadata might stomp on your (slightly) custom type
Yen:570
Free:0
AuD:5.70
USD:3.99
The thing with identifiers is it really is 2 parts. The type:value
They are also selectable in the Tag Browser