Obviously Snap-On, Matco, and Mac make most of their own boxes, as far as I know only for them. Kennedy made boxes for Conrwell at one time. Id like to say Waterloo Magnum was identical to the SK pro boxes a while back, looked identical to Craftsman Professional. Quality Craft makes OR distributes boxes for Montezuma, Extreme, Menards, ect. I do not know if Lista makes boxes for others, I would say probably not.
Frankly I don't care unless its a complete rebadge. I've designed lots of sheet metal parts that I've had made by various sheet metal houses. It is my design though that makes it different from the parts made there by other customers, not who makes it.
Its not like Snap-On's press brake makes better parts than Waterloo's. If they are designed to be cheap, or designed to be top of the line, they will turn out like they are designed assuming the manufacturers are capable.
My company does some contract manufacuring as well as making our own products. We build it exactly to your drawings. If you design an item that is sloppy and cheap, you'll get exactly what's on the drawing.
Now if they are making the boxes by the same drawings and process routing, and half get pained red with one badge, half black with another company's badge, and half blue with yet anothers badge, then you've got something to consider.