John Deere called them a "furrow filler". A smaller diameter blade that helped fill in the furrow caused by the last full size blade on the outside of each rear gang. 2 piece bracket clamped onto a special washer on the disk gang.

This looks similar to the ones found on a JD  AW model disk.

Would need to verify that the dimensions are correct and they are interchangeable.

JD part drawing, number's and pricing for reference.

(AW 1 (full).JPG)

(AW 2 (full).JPG)

(AW 3 (full).JPG)

AW 1 (full).JPG (40KB - 106 downloads)

AW 2 (full).JPG (20KB - 107 downloads)

AW 3 (full).JPG (19KB - 100 downloads)