Well, I guess you will have some problems then. The thing is that this part doesn't exist.
I had three 1800s and none of these had that part. It is not in the service manual as well. Obviously the 1800 doesn't need it due to another mechanism.
By the way, this is about my 1800, isn't it? So you still have the same problem I had? I also had no idea how to adjust that arm properly. .