Brazil Artwork Repair

The problems with attempting to redo the artwork can be tricky. Here is a tiny example:

This is the only reference image I have to work from. Note the small white box in the center - presumably an ice chest.

On my backglass, this is what it looks like:

My problem is twofold. The shadow and the lines. Projecting the lines gives me a incorrect perspective:

The leftmost lid line is not the same angle as the bottom right box line, everything looks wrong. So how much do I faithfully follow what is there, and how much is the result of a paint chip sliding around or missing pieces.

The shadow is another issue, the notch at the bottom left looks like it is supposed to be there, but I am not so sure about the one at the bottom right.

With a little fudging and nudging I was able to recreate what I think is about what it looked like:

I tried to duplicate the original artist's imperfect style, with wobbly lines and all.

Now on to the next object in the restore......