Copper is not always required to be listed as an ingredient, depending on how much or how little is in the product. Per the MSDS the ingredients for HTH Dual Action 3" chlorinating tables are:

TRICHLORO-S-TRIAZINETRIONE 90 - 96 %
Copper Sulfate pentahydrate 1.4 - 1.55 %
Aluminum sulfate 4.5 - 4.9 %