The DieHards sold in the last 15 years by Sears were either EP or JC, the product number had the EP or JC at the beginning, the EP usually costed a bit more for the same size battery. There was also a regional thing going on like with Walmart, here there are no EP they are all JC and not very good.
Great. That doesn't mean that EP was making Diehard batteries for Sears since the beginning, because they weren't.