Elgin 685 Adive

[Tudor405]

I have just acquired an Elgin watch with a broken 685 movement. This movement has a double sweep second wheel situated on a pinion attached the third wheel arbour through a jewel in the top plate. I appreciate that double wheel arrangement is designed to control the indirect sweep hand stutter. My problem is that should I be able to find a donor movement I cannot see how to install this arrangement. It would seem logical that the train wheel s are installed in the usual way leaving the top pinion protruding and then the double wheel arrangement fitted but I cannot see quite how this should be done as the part retaining the wheels do not appear to want to come off the pinion

Any advice would be welcome. I attach some photos of the offending part. As you can see both the top and bottom pivots are snapped.