Mark I Travel Machine

The Mark I was the name given by Davros to a Travel Machine prototype, the casing of the first Dalek that he created. It was 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)

According to another account, Davros' chair was the Mark I, and his initial 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)

History
Meeting a young Davros before the accident that scarred him, the War Master realised the ideas of what would one day become the Dalek travel machine were "already forming in [his] head". (AUDIO: From the Flames)

The first Mark I Travel Machine created by Davros hosted the brain of Baran, a captured Thal spy. (AUDIO: Guilt)

Davros' claims to have designed the Daleks' travel machines were later contradicted by the Daleks themselves under the command of the Dalek Prime, who instead claimed that he had stolen the designs from other scientists and then passed them off as his own. (PROSE: War of the Daleks) Indeed, in one account, the very first Dalek casings were originally the "Dalek War Machines" designed by the scientist Yarvelling for use in the war against the Thals before the mutated Daleks claimed them as protection against the harsh conditions of the devastated, irradiated Skaro. (COMIC: Genesis of Evil) Nevertheless, there were many other accounts that credited Davros with the invention of the casing. (AUDIO: From the Flames; PROSE: The Whoniverse, et. al)

Behind the scenes

 * "Mk I Dalek" is the fan name given to the first model of Dalek casings, as seen in TV: The Daleks and COMIC: Genesis of Evil, some of whom were also seen on the restored Skaro attending to the dying Davros in TV: The Magician's Apprentice. They are distinguishable by their lack of slats. In this terminology, the "Mk II" is the Dalek design with the dish from TV: The Dalek Invasion of Earth, with the "Mk III" — tying back to the designation of the standard Dalek casing from Genesis of the Daleks — being for the one with slats first seen in TV: The Chase. Within in-universe sources, however, there is little room given for Davros' Mark I Travel Machines to correspond to the Daleks in The Daleks, as the clear intent behind Genesis of the Daleks was that it took place prior to The Daleks. The term of Dalek War Machine is given instead, in COMIC: Genesis of Evil, as the original name for the casings seen in the first few Dalek television stories. The Dalek Combat Training Manual would later name the "Mk I" and "Mk II" Dalek models as Type I and Type II.
 * The Davros Connections documentary depicts what the Mark I looks like in an animation matching an extract of the "Guilt" audio. In it, a black sphere on grey skirt colour scheme was used, no actual top casing existed but only a bare metal framework over a green mutant linked to a green luminescent sphere behaving like a Luminosity discharger and an eyestalk.