As I sit here waiting for my first 1894 to arrive, I’ve been killing time lovingly staring at the photos from the auction…  What is the formal name for the screw that I’m missing?  I’m assuming it serves as a stop for the slider, but I need to know what to search for so I can replace it.  Having a bear of a time finding a parts diagram for it.

Also, any recommendations for a source (reproduction is ok)?