Bedside toolbox hinge bolts?

[Davidf]

So, I finished rebuilding the toolbox door and opening. The bottom flange of the opening is doubled up with 16 gauge sheet metal. My question is what bolts were used to fasten the hinges to the flange?

Were they sheet metal screws? Self taping machine screws? Are they supposed to be captured nuts (or welded) on the backside for machine screws? Then what type of head on the fastener? And what type of head on all the sheet metal screws around the perimeter of the box?

[Davidf]

My tendency is to use #10 flat head sheet metal screws everywhere. But, still not sure what was factory original.