The group's motor-driven fourbar with a symmetrical coupler curve (L3 = L4 = BP). One crank revolution drives coupler point P around the oval. A rigid lazy arm with a weighted moist tip hangs from P on a free pin: it trails as it drags the top page toward the spine, and the page flips over once the tip has carried it past the spine.
Book: 13.5″ wide open (6.75″ pages), 9.5″ deep, pages curled to 0.75″. The arm is a rigid rod on a free pin with a weighted tip and some pin friction, so it swings but settles quickly. It is long enough that P stays outside the half-circle the 6.75″ page sweeps as it turns. The oval sits so a hanging arm would reach 0.4″ below the top page curl, which makes it lean back while it drags. Its stroke is longer than the open book so the tip runs off the far edge of the flipped page before it lifts and turns back. The page flip itself is animated, not a paper simulation.