GMG's ProofControl is Quality Control System

GMG's ProofControl quality-control system documents every proof with a
specific identification number, giving print providers a secure customer record of approved proofs. The ProofControl system consists of
ColorProof software (color engine, profile editor/creator, Fogra Media
Wedge, and RIP), a Gretag spectrophotometer, and output modules for
various printing devices.

Using the included spectrophotometer, the Media Wedge is measured and
the resultant values are compared with stored target values. For all
proofs within tolerance, a small adhesive label is printed on a label
printer, which is also sold as part of the ProofControl system. The
label, which contains all relevant production information, is then
placed on the back of each calibrated proof, marking the proof as having met color standards. (GMG: www.gmgcolor.com)