Repainting/Touchup of Craftsman Steel Tool Boxes

In prepping for moving, I’ve been going through several Craftsman gray steel toolboxes that were my father’s, father in laws, or mine. A couple of them are showing some rust on the bottom, but there is no structural problem. I would want to touch them up on the bottom to prevent the rust from spreading. Anyone know what paint would match pretty closely? These boxes are all at least thirty years old, so they are of the vintage Craftsman variety.