The top line in your image seems to be in the same position as box_silver_upper.tga in my interface, but I don't find that file in the official skindef or files. It's very probably my error since I'm not good with removing unused files, but it seems to be displaying anyway.
I don't know what to make of it. I only mention it in case you're desperate. Good luck. The line in my skindef:
<Mapping ArtAssetID="box_silver_upper" FileName="boxes/box_upper.tga"></Mapping>