A friend of mine has a Baywatch where the button fell out/apart. He sent me the pieces and asked me to reproduce the broken part. Attached are photos of the pieces put back together the best I can from the parts. Also attached is the cad drawing of the replacement. I have questions about it I'm hoping this group can help with.

Where does the broken part go? My friend didn't get a look at it before it was broken and pieces were scattered. By looking at it I presume it goes behind the button with the nut around it to hold it in. If so I'm puzzled why are those notches there. Anyone know why they are there and if they are important? If they are important then is the size/shape important? It's a very specific design so I can't imagine it's not important in some way. It may be a repurposed part but I can't find what it's based from. Thanks!

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