User blog comment:12th Supernova/750 chapters is a LOT/@comment-3425840-20140618154341/@comment-71.13.82.190-20140618185157

You make a point that the cuffs have seastone but not the chains, but that doesn't matter as then Robin would still have been stuck with the cuffs on. This only works if we start making assumptions that he switched them before or after breaking the chain, which seems silly when he could have just removed them with his powers instead of switching them and then breaking them.