Usually, for a closepack centre design, a "py" cane in the group is fairly easy to spot.
If there is nothing that, from a close distance, looks like a multi-colour "filler cane", then it is very probably an unsigned weight. If there is something that looks like a "filler cane", always check it out thoroughly.
I once bought together two small PY star pattern weights, one of which was sold as being signed (but with a crack in the base) and the other as good condition but unsigned. When I received them, I found that both had a "py" cane, but one was so small and set between the edges of two "cane group star arms" that it was not noticed.