Switching on and we immediately notice that "Acorn" appears in capital letters on this machine. This isn't some kind of system fault, or anything to do with this machine being a Master 512, but in fact the modified start-up message for machines running MOS 3.50.

All Master 128 machines were fitted with the system ROM containing MOS 3.20, but in 1989, Acorn issued an optional upgrade ROM containing MOS version 3.50 and updates to the other utilities in the system ROM. This was never fitted as standard to Master 128 machines, apparently due to compatibility problems with certain software, so it was only ever fitted as a user upgrade.