This looks to me unsuspiciously like one of many European coppers that circulated in England in 1876 and surrounding decades. Some famous (i.e. common) ones are PEAR'S SOAP and BORWICK'S BAKING POWDER. Such British Isles counterstamps on copper and bronze coins, both merchant pieces and others, are cataloged in a book by Gavin Scott.

It became illegal to deface British bronze coins. (Smaller coins in bronze replaced the earlier coppers, beginning 1860.) However, Continental "5" and "10" coins --Centimes, Centesimi, Stotinki, Para, etc.-- were issued by Latin Monetary Union countries. These circulated in England, where they were just about the same size as the Halfpenny and Penny bronze coins. Advertisers stamped them and put them into circulation.

This piece may relate to a British product that won an award at the Expo in Philly. At this time, I haven't been able to check if Scott lists it. It may be some kind of trial, never issued in an effective quantity for advertising. These kinds of pieces were not stamped on both sides, so this anonymous piece does not make sense. Nonetheless, it very much has the right look for inclusion in the series in question.