Truck Question

Its the collector truck for a Postwar Lionel ALCO diesel.

Some have a mounting stud riveted to a similar sheet metal top plate. Those trucks have either an e-ring or horse shoe washer to retain the truck

Your truck has the mounting clip die-cut out the top plate and bent upwards. Most of the ones I've seen have an external retaining ring holding the truck on.
Stick the tab through the frame's mounting hole, and put the retaining ring in the groove.

Your truck looks like the tab may be bent.

I may have one in my parts bin. If I do, I will post a photo.

Off the top of my head, I cannot tell you exactly which ALCO's had that exact truck. 

Here are some pictures. The external retaining ring is an original Postwar Lionel factory part.

Thanks for the Pics. This truck came mounted in an old 1055 I just acquired, the truck looks correct except when I opened it up it looked like what C.W posted above. I own a few 1055/65's and have never seen them with a truck like this.

I think some switchers had that truck too. Probably the 635 and/or 645. I will have to check.

They were also used on some "B" units, and/or some dummy "A" units. Notice that there is a second mounting tab punched out, but not bent up. One of the trucks on those units needs to have the post in a different spot, and at a different height. I'd have to check the junk drawers to see whether it was the dummy "A" unit, "B" unit, or both.