master copy

(publishing, printing) 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).

(business) 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).

(fine arts) A copy from a master (a copy of a masterpiece), done for reasons including training, enjoyment, homage, pastiche, or otherwise.