Right. There's another version of this PCB - some who've obtained one recently may have it. You can easily identify it by the mysterious extra hole (via to nowhere) I've circled in green in the first picture... There are a couple of other differences too, but that's the most obvious.
There's a problem with the traces on the board (Pin 4 of the LS10 should be linked to A12, it's not, it's actually linked to something else that I can't be mithered to look up). The fix is pretty straightforward. Cut the track I've circled in red (component side):
Then on the solder side use some hookup wire to connect pin 4 of the LS10 to the via I've circled in red:
Job done, working peg. Hooray
- (Richard T will be pleased, it's his board!).
The perils of old mystery stock, but I like a puzzle that has a happy solution...