I've seen that pin before, but I'm not sure what it is. There is a line drawing of it on page 298 of the book "The Legacy of Gamma Phi Beta" in the section which describes the various "non-official" gift items which have been sold over the years. The Beta Lambda chapter advisor over at SDSU has one and I saw her wearing it during recruitment. I overheard someone asking her what it is, but I didn't hear the whole answer. I remember that she implied that it was given to her as an award and so she thought she should probably wear it. As far as I can tell, it's not a major international award pin or anything like that, so I assume you could wear it whenever you like!
.....Kelly