Non-fungible

Horses, slaves, and so forth, are non-fungible things, because they differ individually in value and cannot be exchanged indifferently one for another.

Roman law draws a distinction between fungibles and non-fungibles which looks superficially the same as the thing/wealth distinction but is in fact different. A thing is fungible if it is not unique, in the sense that, if lost, it could be replaced by a thing that is to all intents and purposes identical.