As I mentioned several days earlier, I had a "new" AA Lionel 6-18901 set that I'd mailed to CA. During transit, the screw hole on the E unit bracket gave way and let the lead weight smash into this and that. Luckily, I now have parts on the way to refasten things. The reason for the post is to suggest that if you are mailing such a set with the electronic E unit in the dummy engine, I would suggest taking it apart and anchoring the lead weight with a short length of duct tape, or taking the weight out all together for mailing and place it in one of the "holes" on the ends of the styrofoam if you're using the original box for shipping. Plastic can get brittle with age and the outside edge of the screw hole is quite narrow. A few sheets of Kleenex stuffed in the shell will keep the electronic board from shifting around as well. (And of course, you should let the person you are mailing it to know what should be done on receipt and how to put it back together.)
I am contemplating not using the original "wood" screw and instead use a longer and slightly smaller (so it doesn't chew into the plastic to make threads) machine screw, washers and a nut to hold everything together. This might reduce the stress on the plastic for a more permanent repair.
I don't know whether this arrangement was used in other Series of diesels during that period but it is possible. I had never taken out the dummy unit to inspect it after I bought it, so I don't know when the breakage occurred. But if you pick one up and hear something heavy sliding around that shouldn't, this is possibly what has happened.
Thanks to John Severns for his help in getting this problem resolved quickly. (He does have the tray that had the screw hole break that anchors everything.)