The Marvin Hex head screw is used to hold the pull handle to the escutcheon plate.

Marvin 10-32 x 7/16 inch or M5 x 12mm Truss Head Handle Screws.
A handle set has a total of 4 screw in box, 2 for each handle.
Material: Stainless Steel

If you need a replacement, the 10-32 x 3/8 is available at most hardware stores.
Do NOT get the longer 1/2", it may be to long and damage the plate.

Priced and sold as each.