This is a pencil holder/pen holder for an Edsal shelf or a keyhole shelf.  The studs are 36mm on center and this holder catches 3 of the slots on the shelf.  The pencil holder is 54mm in diameter and the opening is 97mm deep with the entire holder being 100mm high.  This design was made using FreeCAD.  I have provided the .stl, .3mf, and the .step file for you to work with.