Hershey's Special Dark
Special Dark is similar to a standard Hershey bar, but is made with a dark (or semi-sweet) variety of chocolate, and contains a higher percentage (45%) of cocoa solids, chocolate liquor and cocoa butter than milk chocolate. The Special Dark bar replaced the similar, if not identical, Hershey's Semi-Sweet bar in the company's product lineup in the early 1970s.
Hershey's Special Dark is a component of the traditional Hershey's Miniatures assortment first sold in 1939, when the Special Dark was called Semi-Sweet.
In 2006, Hershey's began selling Hershey's Special Dark Miniatures, which included the plain Special Dark bar, along with dark bars with peanuts (similar to a Mr. Goodbar) and with crisped rice (similar to a Krackel).
Hershey's Extra Dark
Hershey's Extra Dark is a product very similar to the Special Dark. The three varieties are solid chocolate; chocolate with macadamia nuts and dried cranberries; and chocolate with cranberries, blueberries, pomegranate, and almonds. Hershey's marketing emphasizes the antioxidant qualities of these bars' ingredients. Additionally, Hershey's Extra Dark contains 60% cocoa solids while Hershey's Special Dark contains 45% cocoa solids.