The earlier post on the 420 oil filter got me wondering on how different the M filter was from the 420. When I looked it up in the parts manual I found parts key #23 was shown in the illustration but not in the parts list, in fact the key doesn't show any number above #16 other than #23. When I used the part # from the 420 parts list it shows up in the M index as a washer in the MC hydraulic control valve. Just for the record I think the washer is part of the newer oil filters anyway. Probably just a glitch but I found it interesting especially since I was aware of sealing plate #8 being discarded with the old filter a lot of times as they stick to it but not aware of washer #23. Bill