It's the piece that locks the coin mech into the coin door. The 2 holes are for the 2 screws on the coin mech -- you back out the 2 screws until they come through the holes, this prevents left / right slippage of the mech.
Here is a link to the coin mech to help with the visualization.
Yeah I was messing around and figured it out late last night. Unfortunatly I only have one and one retaining clip for both coin slots...so I am going to have to see if I can get some replacment parts. Thanks for all the help guys.