The first shows the coil mounted on a cylinder. This proved to be fairly troublesome to make, and I probably won't repeat the exercise.
The second shows a more normal "hinged flap" arrangement, similar to that on my 2mm scale Class 04. This was much simpler to build, and is the basis of a prototype etched component. The "nose" sticking out is a piece of lead which ensures the flap falls when the current is turned off, and the horizontal wire at the top limits rotation to 90 degrees.
The loco isn't finished yet; lots of details to add, and I want to make sprung buffers and other extras which require work on the lathe. So video in operation will be a while coming. But it does all work, the couplers are wired in series to a single function output of a Zimo MX620 chip. The chip is in a paper sleeve below the motor. Both couplers rotate 90 degrees, which is far more than I need to release an Alex Jackson. The Alex Jackson's will be fitted onto the outputs of the mechanisms with a bit of fine bore tube.