Quoted from LTG:
Since you don't know where it goes, and may not even be for pinball. Of course you can leave it off.
If something doesn't work or flies apart - you found where it goes.
That is what cabinet bottoms are for. Crap you don't know where it come from or belongs.
LTG : )
+1 there... Play it until something appears to be odd...
Last week I found an odd 'rivet' thingamajig laying in the bottom of my F-14... Looked for 5 minutes for a home, gave up, and 2 games later when my ball got stuck between the two 'kill' targets I figured out what it was. A target leaf stack rivet.