Throughout the decades in which it produced plastic derailleurs, Simplex struggled with the problem of how to manage the limits on the rotation at the B pivot. The steel hanger plate had a nasty habit of chewing up any limiting 'lumps' on the plastic B knuckle.
This patent is concerned with this issue. The design involved is the late, low-end, cheap, and, lets face it, nasty, B-knuckle used on the Simplex SX1 and Simplex Alpha. A metal flange is shown that can be swung into or out of position, giving the derailleur two possible angles at the B-pvot, I believe that one was for wide ratio freewheels and the other for close ratios. This design did not make it into production. Instead Simplex used a screw based system. You can see it here.