Sentence:  "Resolved", that the Curators be authorized to exchange with other societies or individuals, such duplicate or <WSD>supernumerary</WSD> specimens of coins, medals, minerals and other articles as they may deem unnecessary to be retained in the Cabinet of the Society, for such other specimens, of equal value, as they may consider desirable to be added to the Society's present collection; ... 
Meaning of the word marked with <WSD> tags:  Beyond what is necessary; redundant.