Mark III Travel Machine

The Mark III Travel Machine was Davros's the optimum design for the travel machine to house his genetically engineered Kaled mutants. He would call his invention a Dalek, an anagram of the word Kaled, to reflect the reconfigured Kaled life form within. The term would come to be used to refer to the life form as well as the machine. (PROSE: Dalek Combat Training Manual, TV: Genesis of the Daleks)

Development
By one account, Davros' chair was the Mark I Travel Machine, and his initial Dalek designs were the Mark IIs. (PROSE: The History of the Daleks) Another account had Davros present an early prototype machine before he had constructed his own advanced chair, after which he unveiled Dalek One. (PROSE: Davros Genesis) In any case, the Daleks were later perfected by Davros in the Mark III Travel Machine. (TV: Genesis of the Daleks)

By another account, Davros's Mark I Travel Machine was not his chair but a prototype casing of the first Dalek that he created, an experimental life support unit modeled after his own chair. Besides the transplanted Thal brain, it included a life support matrix, an optical stalk, feeding tubes and was activated by a power conduit with only 92% distribution. (AUDIO: Guilt) According to the Dalek Combat Training Manual, Davros abandoned this prototype and then his next model before settling upon the Mark III travel machine. (PROSE: Dalek Combat Training Manual)

In contrast to the earlier models, the Mark III worked with several different power sources, allowing them greater mobility and not restricting them to the static electrical power their prototypes used. A ring of solar cells was constructed about the midsection of the casing. In cases of need, there would be a battery pack inside the casing. An optional addition, useful for overcast areas, was a small dish that could be attached to the back of the Dalek to collect broadcast power. (PROSE: The History of the Daleks)

Later history
The Time Lords understood that "the original Dalek prototype" had a toughened grey coating, bonded to the Dalekanium shell and black sensor globes. This design was replicated for later design units with variant coatings resulting in different shades of grey. The Time Lords identified nine distinct "Types" of Dalek casing, with the grey Daleks being designated as Type IV following the Type I, slatless silver Daleks, the Type II, silver Daleks with solar energy collection discs, and Type III Dalek, silver Daleks modified with slats. The Type IV was followed by the Type V Dalek, silver Daleks with "multiphase" black sensor globes". In defiance of the Supreme Dalek, Davros himself would creature a new Dalek race, the "Type VI" Necros Daleks, which he refined with the "Type VII" Imperial Daleks. Bronze Daleks were designated "Type VIII" and believed to have been developed for the Last Great Time War, with the Time Lords describing them as the ultimate warrior.

The New Dalek Paradigm established in the post-Time War universe used a new casing model designated as "Type IX", (PROSE: Dalek Combat Training Manual) but a series of defeats at the hands of the Eleventh Doctor led to this casing falling out of favor and being replaced by the older Bronze Daleks, who were deemed by the Prime Minister of the Daleks to provoke the most fear throughout the universe. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)