Spearhead from Space 4 prop reuse!

While watching Spearhead from Space, the machine the Doctor builds to defeat the Autons in episode 4 caught my eye. In particular it was the shiny sphere used in the machine, and the way it was opened up in the lab exposing electronics inside.

I thought "I've seen a silver sphere like that with electronics inside before in Web of Fear!" and sure enough...

A better look at the sphere when it's opened in the factory confirms it's previous usage!