Malcolm -
As can happen so very often with these older belt-drive machines, even with all mounting hardware removed, a part, especially the transmission or basket drive, does not want to come loose (this happens a lot too with the agitators). In this case, Ted was wrestling with the gearcase and it let-go suddenly, causing him to slam his left hand against the edge of the cabinet.
I have a number of those battle scars from older restorations myself, but they can put a damper on the fun!
Gordon