Generation 01 and Generation 04.
Facing numerous defeats at the hands of Davros' Imperial Faction – due in large part to squads of Special Weapon casings being fielded by their foes, the Loyalist requirement for its own, reliable Special Weapon units increased dramatically. Keeping with the original Special Weapon concept, the internal mechanisms of the original design were improved and upgraded. After an extensive testing process, the casing was determined safe for use by pure Dalek mutants. The casing was put into production and Special Weapon units became a common sight on major battlefields throughout the course of First Dalek Empire.
The lower half of the Mark Two Special Weapon casing was identical to that of the Mark One, maintaining the fifty-two (52) sensor globe configuration. The upper half of the casing saw some variation, particularly in the dome at the top of the casing.
This dome was designed to be more reminiscent of a standard Dalek casing. The main difference was that the front sloped in at a sharper angle than the rear, and the sides were straighter. Instead of the usual eye-stalk arrangement, an advanced scanning unit was installed. Data from this fed directly to the targeting computer in the dome, making target acquisition a few micro seconds quicker than that of a standard Dalek. Luminoscity dischargers were positioned flat to the surface of the dome to maintain a sleeker and more elegant design.
Internally, the habitation module located behind the over-sized cannon was reinforced and shielded to provide additional protection to the Dalek creature inside. This shielding not only protected from external assaults, but also acted as a buffer for any radiation leakage that may have occurred from the casing's power feed to the weapon system. Beneath the habitation module, the nutrient tank and its reprocessing systems were similarly shielded.
The specifications of the Mark Two's power generator and motive unit were practically the same as the original Special Weapon casing. The main difference was that the power generator and associated systems were more efficient, allowing the environment sensors to function more like those of a standard Dalek unit. Occupants of the Mark Two Special Weapon casing were able to work more independently, allowing them to be used in a more tactical manner on the battlefield. The motive unit still struggled to allow the unit to keep up with standard casings, however.
The Genocide machine. This is a conjectural design and is an attempt to bring the Special Weapon casing more in line with the aesthetics of Dalek design