A watermark and extracting method and a watermark hardware structure used in an image compression system. The invention further provides for Archaeal DNA polymerase mutants with deficient 3\u2032-5\u2032 exonuclease activity and reduced base analog detection activity containing additional mutations that modulate other DNA polymerase activities including DNA polymerization or reverse transcriptase activity. The keyboard also includes a first key return spring configured to apply a return force to the first key to bias the first key toward the rest position. Locations of edges of the plurality of regions are determined A common location is determined from the determined edges. The clock signal to each module is further passed through a locked oscillator, which will continue to maintain the clock signal should the master clock signal fail. The holding member includes a holding part for holding the wear plate and a fixing mechanism for releasably fixing the holding member to a vertical wall segment of the rotor such that the wear plate bears against a first side of the wall segment.