A review for Circle stickers by DonnaBarr.
First of all, this is us: https://www.facebook.com/events/371666649623280/
Attendees were whining they couldn't prove they'd attended, because we have no admission fees or stinking badges.
Now they can prove they attended! Table bosses and panel moderators get a sticker. Everybody else buys one for a dollar.
Problem solved. Thank you, StickerMule! Hee Haw!