The layout and connector reminds me of the TM5000 series plugins - but it looks a bit bare - presumably it's for a relatively simple plugin - you could examine some service manuals for - I looked inside my FG5010 - that board runs right to the front of the plugin to interface with the rest of the gubbins and homes a CPU with support logic and ROMs... I only have one other type of plugin for the TM5000 series... Though the connector is the same, the DIP switch bank on my FG5010 is below the connector and only has 6 switches - so that could be a bit cramped.
I think that some 11000 series plugins had GPIB but I don't know them...
bill K7WXW