Rectangular plates. The cast lead alloy pillars have square ends. The oldest movements I've seen are like this.
Plate Shape 2: Cut corners:
The balance end of the movement has both corners cut off with a straight cut. This is the second type of plate shape. Used through ca. the mid to late 1890s.
Plate Shape 3: Cut and Stepped Corner:
One corner is straight cut, and one is step cut and has a square corner next to the balance for a steel pillar to reinforce the movement. One early example of this has no steel pillar. Used starting ca. mid to late 1890s.
