master copy

Noun

 * 1)  The copy that serves as the controlling (master) version among a set of copies (as, for example, the master proof to which edits from the authors' proofs are transferred, or an analogous master manuscript with transferred edits).
 * 2)  An original instance—copy of a document, copy of a digital file (or, metonymically, the disk that contains it), stencil, or otherwise—that serves as a controlling version from which duplicates are made (such as photocopies, printouts, mimeographs, transcluded instances, static content forks, stenciling impression instances, or otherwise).
 * 3)  A copy from a master (a copy of a masterpiece), done for reasons including training, enjoyment, homage, pastiche, or otherwise.
 * 1)  A copy from a master (a copy of a masterpiece), done for reasons including training, enjoyment, homage, pastiche, or otherwise.

Usage notes
Most of the terms  and  have the semantic notion of "the copy that is the master version", but the fine arts sense of the terms instead has the semantic notion of "a copy of the master version". This sense difference puts the pair into the class of contranyms, albeit it a little-used example of that class.