Yep, definitely an Ab box on the pull, which is the key of Eb. The chord progression repeats one bar of Eb followed by one bar of Ab, then it hangs on Bb for 4 bars at the end of the bridge or whatever you want to call it.
A long time ago, he was playing one of our local dances and he asked me to sit in for a couple songs.
The accordion was in Ab, and it might be the same one. I remember my thumb was swimming in the thumb strap - I have big hands, but I guess not as big as his.
I have an A box, so, should work. I have a similar vocal range as geno, so when he does something to dodge a high note, I usually can't hit it either. In Jeunes files DE LA campagne, he misprounces campagne (compawn) because that allows him to hit it. I just do it in D on my GC box.