I have taken away the ribbon cables to show everything and we can see that the circuit board has been slightly rearranged from the E01.

We can see the 2793 floppy disc controller, 65C102 processor, 146818 real time clock, 6522 VIA and a single control ROM.

The host adapter interface to hard discs is built into the circuit board just below the FileStore Bus connector at the back of the unit.

Here we have another interesting example of what Acorn actually call their machines - the E01S is known as the "FileStore II"