Here a link to Bryan Kelly's resto video of an MM coindoor, system 11 stamped steel doors get the same "spatter" finish. This weekend I'm repainting my first sys 11 door for an Earthshaker and I just tested out his method on some scrap metal, damned if it doesn't look super close to the real deal.

One addition I might make, courtesy of CosmoKramer, is to chill your gloss black spray paint in the freezer for 15 minutes or so prior to painting the spatter. I found that at room temperature I was getting too fine a spatter pattern, and chilling the paint a bit made the globs a little larger and closer to the original finish.