This picture shows the Econet interface inside an MDFS. It is located in the bottom-left hand corner of the main board, or the top-right hand corner of the MDFS file server unit.

The Econet interface in SJ Research file servers is unique in not being based around the Motorola 68B54 controller. I think this is because the MDFS is not 6502 based, instead using the Z80 processor.

There are spaces for additional components and links and I wonder if these were for adding a clock generator. This would have really set off the MDFS as the all-singing and dancing Econet file server if it could provide the Econet clock as well!