Two small straight edges, a square and a planer gauge.
The two rods should unscrew from the wooden carrier and screw into the planer gauge (one at a time). Probably 1/2" difference in length between them. There might be a third, quite short rod in the top rightish of the box but not in the exploded diagram.
Edit: We hope he was better at metalwork than he was at putting hinges on boxes.
Very nice bits of kit for that once in every ten year job that requires them, I'll bet we all have bits like that in one form or another, I know I do...