Vansell's TARDIS was a modified and unregistered Type 70, which he used on his CIA assignments. Due to it being unregistered, the Chancellery Guard briefly believed that it was stolen.
Vansell travelled in his TARDIS to meet with the Lord President and inform him of the Knights of Velyshaa's imminent invasion. After the Fifth, Sixth and Seventh Doctors thwarted the Sirens of Time, Vansell exited his TARDIS and was unable to remember why he was there, prompting him to return to his TARDIS and leave. (AUDIO: The Sirens of Time)