Not exactly sure ! Of course the best way is to visually inspect them to know, sort of hard to do until it's apart. Not sure if a bore scope through the grease plug up top would allow you to see this or not ?

I'm guessing whatever year Deere offered knife rolls as OEM option from the factory. There seems to be a lot of confusion by exact serial numbers  and of course some were converted to knife rolls without having the gears updated which is what I've ran into.