The "black stuff" appears to be the original finish - it definitely is not dirt.
Since this box is FUBAR as far as preserving the finish - they appear to have sanded it down on top - I tried various solvents to see what remelted the finish. Scraping the black stuff until I an see the wood grain emerge and then melt seems to be a good compromise. I didn't have any lacquer thinner handy but carb cleaner seemed to do the job but was too volatile and dried too soon - but there was gloss in places that looked good. So I'm close.
Let me step back and state my objective: this box was out in my partially enclosed carport along with other tool boxes, etc. where I work on projects and don't care about keeping stuff clean. However I want to bring this into my home and put clean electronic repair tools in it. Very clan stuff. The finish is just too nasty so I need to do something. To what extent, I will not remove any of the hardware to do this job. I'm looking to spend 1-2 hours on it.
SECOND biggest worry is the drawer felts since they have metal chips embedded in them. That is a real No-No. I was thinking of replacing the felts but then realized there were sides to do on top. Although I have the felt already, can't afford to spend the time right now.
Pulled most chips out with shipping tape, then soaked and brushed with Super Clean Purple degreaser, sprayed off in sink, let dry and then hand picked remaining chips out. MAYBE I might pull the bottoms out and replace and do the sides and tops later???