One of the brakes. What strikes me as odd is the place of the bleed nipple. This is in a different (and more logical) position on the parts car.
Also note that the later type of bleed nipple doesn't use a ball. It just has a small hole on the side that allows you to bleed the system when released.
Looking at the parts list drawings it seems that somebody, indeed changed the place of the cylinders. The bleed nipple should of course be on the wheel side of the car. In the service manual it says the "hairpin bend" in the tubing shoud be on the inside. That's the case here but it's not in the correct hole, the brake piping from the axle can't be connected this way. So did somebody mess up?