Roots: Blade Runner "More human than the humans". Two'Mark's worker drone forklifts are called 'Rambos', the works of Asimov (positronic brains)
Intertextuality: The identity (such as it is) of the agent Corvus is revealed in the Cyberman 2 episode Machines.
Technobabble: Androids have positronic synth neural architecture and magnetic bubble memory
Continuity: The mechanic Two'Mark recalls seeing a horror movie about the Orion War (it was a musical). Nearly two thousand years after the war there are still millions of self-repairing androids from Orion that are still working. A Grade 3 intelligence robot is only useful for loading and shifting crates - nothing more than a talking fork-lift and able to follow very basic instructions.
Station Sierra-Five was a warship dry dock servicing warships like the Sunbow, a neutronic tanker, during the Wars. Kingdom of Silver's android agents here are given the respective identifications Sara (four-six-gamma-three) and Temeter (one-nine-alpha-six).
Android society includes a War Council and Adjudication Tribunal below this. Tribunals prefer not to execute for reasons of efficiency. Instead, subject's mind is evicted from their body, their higher mental functions tripped away leaving only the basic elements of intelligence and their brain is re-programmed for menial tasks. An android's circulatory system includes a central reservoir from which a synthetic processor medium flows through artificial veins (this is the closest androids have to blood). An electro-pulse weapon is designed to kill androids by swamping the neural paths of their positronic brain with electro-magnetic energy. It burns through an android's synthetic cells, nerves and synapses while leaving the victim conscious and in extreme pain to the end.
Agent Corvus is a Cybrid, a modified human enhanced with Cyber technology and masquerading as an android. His ship is capable of hyperspace travel; Corvus manages to steal a portable bio-morph unit, enabling him to alter his physical appearance.
According to Two'Mark the greatest design fault in the Type Forty TARDIS was the fluid links (he says the Type Sixties never had that problem). The Doctor says he prefers the 'classic model's more refined lines, and the TARDIS interior's roundel style to the Gothic overhaul, although his favourite is still the coral version).
Q.v. 'The Orion War'
Links: Kingdom of Silver. The fate of the double agent 'Corvus' is revealed in Cyberman 2. Time Crash (the coral TARDIS interior).
Location: A salvage yard nearly two thousand years after Kingdom of Silver.
The Bottom Line: "Organics, synthetics - who can tell the difference these days? What's the point of going to war over that, eh?"
Something of a prototype Companion Chronicle in its narrative style and subjects, Keepsake uses some of the monologue nature of the Cyberman series to tell its story, bookended by the Seventh Doctor's discovery. It's a touching tale, though some listeners may be bothered that it is not entirely followed up in the second spin-off series.