Space capsule (The Power of the Daleks)

A space capsule crewed by three silver Daleks crash landed in the mercury swamp of the planet Vulcan. (TV: The Power of the Daleks)

Origins
According to human historians in the post-Time War universe, the capsule was a factory ship, one of thousands sent out in the early days of the Dalek Empire. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) According to the Time Lords' Dalek Combat Training Manual, it was a scout craft used for reconnaissance missions. Intelligence further identified it as a short-range exploratory vessel, explaining its crew's reliance on static electricity. (PROSE: Dalek Combat Training Manual)

During the renewed civil war between the Daleks loyal to the Dalek Prime and those loyal to Davros, the former faction planted a dimensionally transcendental factory ship aboard a Thal ship returning to their own space. This was discovered by the Eighth Doctor who, aware that this would enable the creation of a new Dalek army in enemy territory, used the TARDIS to expel the factory ship through interstitial space, claiming that he had already dealt with it "in another time, and another place." (PROSE: War of the Daleks)

On Vulcan
In a transmission recovered and recorded in The Dalek Conquests, the capsule was on a course which entailed traversing the orbital path of the planet Vulcan when its engines were hit by a meteor strike, disabling maneuvering controls. As a result, the capsule was caught in Vulcan's gravitational pull. Though the Dalek crew attempted to transmit a distress signal to their home planet, Skaro, they found that their transmitter was non-functional as main power shut down, leading to a crash landing on Vulcan. (AUDIO: The Dalek Conquests)

Two hundred years later, a human colony had been established on the planet Vulcan. The Daleks were found in their space capsule underground and then reactivated by a scientist called Lesterson. This overlapped with the rebellion against Hensell led by Bragen. The rebellion failed after the Daleks began an indiscriminate slaughter of the colonists but the Second Doctor overloaded their temporary static circuit from the colony's electricity supply. (TV: The Power of the Daleks)

Legacy
Human historians following the Siege of Trenzalore observed that the Dalek factory ship that landed on Vega 4 was significantly more advanced than the capsule found on Vulcan, containing the raw materials required to build over 3,000 Daleks. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

Behind the scenes

 * The Discontinuity Guide claimed that the ship was one of those which escaped the destruction caused by the Dalek Civil War on Skaro before crashing on Vulcan in the 21st or early 22nd century, preceding the 22nd century Dalek invasion of Earth. It is further noted that, since the Fourth Doctor inadvertently changed Dalek history so that Davros survived, this event would have occurred vastly differently if it happened at all in the new timeline.
 * The Dalek Handbook claimed that the capsule was a timeship which fled Skaro in the Civil War, which is dated to the 41st century, before crashing on Vulcan in the past, explaining how the Daleks recognised the newly regenerated Second Doctor but were themselves not recognised by the humans.