This machine has an Issue 2 motherboard and it is the first Issue 2 I have ever seen. There are quite a number of differences between this issue and the more common issue 4 or 7. The machine has been fitted with disc and Econet interfaces and it also has a 16K sideways RAM module in one of the ROM slots. This is attached by a wire to one of the pins on IC77, just above the "Acorn Computer" mark.
I suspect that this BBC may have started life as a Model A and been upgraded to a B later. The soldered-on chips are all dated coded late 1981 and early 1982 but all the chips in holders have later dates during 1983. Certainly the disc and Econet upgrades were added later but the fact that the Operating System ROM, User VIA and Analogue to Digital Converter are all dated 1983 suggests that this is an A-to-B upgrade.
In the pictures above, you can see the copyright mark and the sideways RAM module sitting to the right of OS 1.20, BASIC II and DNFS.
I have a brand-new Econet station in the making here, but I will need some of the jumper links to set the station number. At the moment they are missing and it comes up with "Econet Station 000"!