This is a scan of the Acorn System 1 User Manual that I found a while ago in the internet. For anybody building a replica of this machine and using the official Acorn System 1 Monitor ROM, this manual is invaluable.
There is also a copy of the Acorn System 1 Monitor ROM that I use in my development system. This is an original version with NO code changes. It’s been formatted for use on a 28C64 EEPROM, but should be suitable for any 64K (8Kx8 ROM device)