Theory No2, I'm no frame builder but that's quite a long lug, could the hole have been a way of getting the brass in to the joint?
You should in theory be able to draw brass and silver long distances using capillary action, so would be quite unorthodox, but not a stupid idea at all.
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Theory No2, I'm no frame builder but that's quite a long lug, could the hole have been a way of getting the brass in to the joint?