Ferranti Magnetic Drum, circa 1961, used for secondary storage with a capacity of 16,000 words. Magnetic drum technology was a precursor to the magnetic hard drive; both used used a spinning magnetic surface that could be read or written to by sets of fixed read/write heads.
In the photo, you can't see the drum on the interior, but you can see the read/write heads on the long axis of the drum cylinder and which are connected to the thick white cables running around the base.