That Pfaff 230 is a great example of how that can happen with old Pfaff machines. Look at the pics. There's a motor mounted on the back, and a little 1/8" belt that drives the flywheel. there's a knee-bar controller for cabinet mounting (yeah, it's been pulled from its cabinet).
Now here's a Pfaff 230 that has been set up as an industrial machine. Under the table (industrial machines are always mounted to a large table, not a cabinet) is a huge motor that's always running, and a foot-clutch controls whether power is delivered or not. The flywheel has been replaced with a pulley that takes a standard 3/8" belt drive, and there's no built-in motor. There's also a knee-bar that raises the presser-foot (and is obviously a stock item; if you look at the picture of the back of the machine, the linkage is color-matched with the Pfaff beignze paint and mounts to a pivot that can be seen in the back of the home machine) that's pretty much standard equipment on any industrial sewing machine.
So same head. Industrial, not industrial.