A replicated check disc is pressed from the stamper that is based on the supplied master. It will be identical to the mass order that will be produced from the same stamper. So what is the difference between a replicator and an authorer's check disc?
Most DVD authorers will burn a DVD-R to show clients an example of the work before submitting to the replicator. Menu buttons, navigation and so on can be verified.
On DVD-9 or titles that require copy protection, the master copy will be on DLT (Digital Linear Tape). In this case the authorer will most likely shrink the content onto a single DVD-R or a DVD DL. This check disc will not be a true representation of what the clients will receive from the replicator. Therefore, a check disc from the replicator is highly recommended for DVD-9 and titles with copy protection.
Creating a check disc takes time however. After a stamper is made a few discs are pressed and mailed to customers for approval. The stamper is usually taken out of production and additional setup time is required to finish the job when the check disc is approved.