That's interesting. Just snapped a pic of my -- I think -- original screw and now see that there is a clear plastic or similar sleeve on the underside, apparently serving like a washer. It makes sense that someone adding a replacement screw would use a washer, and that there's no need to do so with this type of screw.
My pic is here: https://drive.google.com/file/d/0B1VBmhfX0CeaZTBmV2RqTWZBcDA/view?usp=sharing
Cheers,
Spencer
My pic is here: https://drive.google.com/file/d/0B1VBmhfX0CeaZTBmV2RqTWZBcDA/view?usp=sharing
Cheers,
Spencer