The Dor-o-Matic 2090 Backplate Assembly PB89 has been around since the early 1970's. It is now called the Falcon 2090 Back Plate Sub Assembly, but it is the same thing, just different owners of the company. This piece includes the plate casting, latch bolt, pinion gear, and retractor.
Doromatic Part # 4270902974 Right Hand
Doromatic Part # 4270902968 Left Hand
LEFT HAND BACKPLATE SHOWN