[Model51]

One final comment. Notice the part number ends in -A2. To me this indicates that there at least two versions of -A. I've only seen this nomenclature when there are two versions of the same part from two different vendors. It's likely that the -A1 version is plywood and the -A2 is assembled from hardwood pieces. Again this is more of my speculation since I don't have a copy of the -A1 drawing or any of the release cards which would likely definitively provide the answers.

At this point I'm not sure that anyone would which version was used especially since this part ends up not visible unless you take the seat out of the truck and flip it over.