Thanks everyone. I wanted to do a reveal with a difference
I usually wear a broach for this and thought the pin would be a little more subtle, although it's quite chunky and robust. My worry, of course, is the back popping off without me noticing and it falling out exposing more than I would like. I'm a tutor and my delegates are usually men, so it might be popular but rather embarrassing. I do think a broach with a clasp is more secure.
Has anyone got any experience of pins and how secure they are?