The D7 class Klingon battle cruiser was used during the 2256 Federation-Klingon War.
One of these ships fought in the Battle of the Binary Stars in 2256. (DIS: "Battle at the Binary Stars")
Later that year, a ship of this class intercepted a shuttle containing Starfleet Captain Gabriel Lorca. (DIS: "Choose Your Pain")
Following the conclusion of the war in 2257, these ships are retired from service in favor of a new design. (DIS: "Point of Light")
According to Star Trek: Discovery The Official Starships Collection, this class of ship is called the Sech (Torch) class.