Charlie,
I see what you mean. I think Dave is right. At first, I thought it was a way to limit the travel of the truck so as to avoid breaking off the wire inside the tender, but it's in the wrong place. I have the link coupler version, but the tender frame is the same, that is, with the little welded tab.
By the way, it looks like the trucks on the tender are the kind used in operating cars with the outside shoe for activation. It's hard to tell in the photo if the trucks have been replaced. Is anybody else's like that?
