Not one of mine, more's the pity, but this baby came up for auction on Yahoo and the seller kindly allowed me to use these pics after the bidding got too rich for my pocket. In fact these are bigger pics than originally posted on the auction site.
So what is it? Well, it's an ARM 1 development board, which gave the BBC range 4MB of memory and an ARM processor to play with. These are extremely rare, and only a few were sold for scientific use; but the reason it's here is that it is the beginnings of the Archimedes 32bit RISC machines Acorn went on to produce (ARM 2 or 3, 4MB of memory).