I always falter before I prevail
lol. I found my info that I needed.
It is a disconnector lever.
It appears as though the model that I have, either use to be or was retrofitted from parts of a fully auto M-1.
It still needs the selector and the selector spring to become a full auto again. (I am not going to persue that at all!!)
I included some pics of the manual for your enjoyment.