I'm an Alpha Phi Omega alumnus and I try to bid on most of the historical stuff on Ebay. (The stuff like the new hat where they will put your name on it is useless).
Alpha Phi Omega is different from most of the social greeks in that the official pin that a brother receives at initiation (and the pledge pin given at pledging) are both *super* cheap - $4 at last check. There are Jeweled pins that are official that can be bought from the national office, but that is the individual brother's choice. The official pins have changed size and backing over the years, so old ones are easily identified on Ebay.
There was a guy who was selling an APO pledge pin on Ebay with the minimum bid of $17, I wrote to him and told him he was out of his mind...
There are about 5-6 regular bidders on Ebay for historical stuff that are brothers, so one (or more of us) are likely to bid on most things, we just have to be sure when we bid against each other.
BTW, for Alpha Phi Omega, one of the really hot things to bid on on Ebay are Scout Patches that mention Alpha Phi Omega since we help with badge days and such...