This story is a rare example of using the dating system of BCE (Before Common Era) over BC (Before Christ).
The Master is in the stolen body of Tremas but not infected by the Cheetah virus. Ace recognises the Master, but it is not clear if this event is before he became infected or after escaping Cheetah World and being cured.
The Doctor uses the alias "Septimus Doctus", despite the Master was expecting him to use "Theta Sigma". (TV: The Armageddon Factor, The Happiness Patrol, et al) The Doctor likewise wonders why the Master doesn't use "Magister", which the Master views as "old hat". (TV: The Dæmons)