This clip is amazing -- I could watch it a thousand more times! (Video from YouTube.)
I am not sure what kind of treble layout Marc Perrone is using in this clip. My understanding is that he had eventually made it easier to play chromatically on the 3-row diatonic (which is already actually chromatic, just not "easily" played chromatically) by replacing redundant notes on the inner rows with "accidentals." Thus, on a G/C/F box, where there are 'pressed' G's on the G row and the C row, one can replaced the C row's G's with G#, and likewise replace the F row's C's with C#. There are also some redundant 'pulled' notes, which can be similarly substituted. For instance, subbing Eb for some of the pulled E's, perhaps on the F row? (Addendum: indeed, the inside (F) row contains Eb's instead of E's!)
At one point, someone (probably in France) had this layout posted on a website, and now I can't find it and am clearly forgetting the details. If anyone finds it, please let me know and I will edit this post, or create a new post about le maitre, Marc Perrone.
In the meanwhile, enjoy this old clip of some truly marvelous box playing!