Been looking again at the pic on Co-Gen. My guess is that resistor has been added, but I’m not sure why. One way to confirm would be to take the screws out of the fixing bracket and see if the holes have been drilled or punched.
My 4.5kva has a small resistor similar to that, against the louvers, and two large ones in the top box. My 4.25, same year as yours, has one large one in the top box and one in the genny but no small resistor. I think the functions are the same, just different mounting areas over the years. I’m not sure why my 4.25 doesn’t have the small resistor.