NENA, the New England Numismatic Association, has issued a medal in conjunction with their annual convention, which they often call a "conference," every year. The obverse varies for year to year while the reverse is the logo of the organization. 
The very first NENA medal was unusual in that it was a large cent with the reverse plained off which was replaced by a design that was etched into the piece with a stamp that had been dipped in acid. 

The Boston Numismatic Society issued this medalet in 1873. It was stuck in several alloys. Brass, silver and copper

1873 TOKEN RULAU MA-BO 13B COPPER BOSTON NUMISMATIC SOCIETY, RB MS66RB

California State Numismatic Association (CSNA), Pacific Coast Numismatic Society (PCNS)

and Sanfransisco Coin Club.......more to come soon