I didn't see your north/south clue at first. As soon as I noticed it just jumped into my head what it was. Try this one:
That's a scale. The extra Globes fit into the left the end where the hole is for extra weight. Length (per the graduations) x the weight would give the force necessary to counterbalance the object you are weighing.
It's not a scale for directly weighing something. The bottom most piece also contains a metal besides brass.