The Acorn Master series was the first computer from Acorn that supported the Econet Module. This was a departure from previous Acorn computers that had the Econet hardware built directly onto the motherboard of the computer. By creating the Econet module, it made the upgrade a faster, cheaper and more efficient job that was no longer reliant on specialist work.
On the Master series then, simply fitting the Econet module and adding a suitable NFS ROM into an available socket such as the ANFS 4.25 ROM is all that is required to achieve a network capable Acorn BBC Master.
This particular Econet Module is the Issue 2 board with full collision detection hardware built in.