Some books I owned.
Ever I had a BBC B+ computer with 64K sideways RAM from Acorn and a 64 K RAM board (one of the designs circulating in the Netherlands) on one of the spare ROM-sockets.
On top of the BBC you see the floppy drives and the AMX mouse.
The inside picture shows the 64K Sideways RAM and the RAM on the spare socket left at the top. Blow-ups over the keyboard. In the ROM sockets the standard DFS and ADFS ROM's are present. The blue switch at the back side (right picture on top) provided write protect on the extended RAM board. Underneath the keyboard was the switch to choice between the two disk-filing systems. The MSX mouse ROM is just to see.
The Acorn upgrade kit contained: the 64K sideways RAM daughter board, the Acorn 64K sideways RAM support disk, the 1770 DFS and a set of instructions how to carry out the modifications.