Hand Made Prototype
In July 2003, I had the good fortune to purchase the two hand-made prototypes of the Master Series Econet Interface made by Acorn.
They are made on Veroboard with all the ICs housed in sockets. There are two rows of pins underneath for connecting to the Master motherboard. Unfortunately, the pins are in different locations to the finished module, so I can't test the prototypes out!
As anybody who has done an Econet upgrade to the BBC Model B would testify, it is an immensely fiddly job involving soldering 7 IC sockets, 20 resistors, a row of pins and a DIN socket onto the motherboard. Whoever thought up the idea of the Econet upgrade as a ready-made plug-in module should have been given an award!