We're asked about this a lot and the answer is simple. Almost all bronze/copper gardening tools are made of bronze (an alloy of copper with a little bit of tin). Pure copper would be too soft.
That said, our dibber is sheathed in copper but then it needs no strength.
So whenever you read or hear about copper gardening tools, you can pretty much assume they are referring to bronze garden tools.
Check out how to care for your bronze tools here.