I believe it's a swelling crack. From one pipe I already retired and a few stories around BoB, often cracks like that start to surface due to expansion from the inside-out--because of moisture. It could be where the tenon ends in the mortise, and if a little post-smoking moisture gets trapped for long periods of time between the mortise walls and some space around the tenon, this can be the result. On my one neat old estate pipe, the tenon was ever-so-slightly narrower at the tip, and that's where the moisture settled. It could be a place where moisture simply collected naturally, or from a botched drilling attempt that was later corrected. Briar being a natural product, there could also be a sand pit or some other blemish internally where it is weak, and again...collecting moisture. Not all briar pieces are as dense or robust, to boot. So it could be one thing or a culmination of things.
One way or the other, smoke it until it dies. That's what it would want. :lol: It may last just as long as any other pipe--who knows? If what is happening is what I suspect, let it dry out a little longer than normal. It might help. <img class="emojione" alt="?" title=":shrug:" src="https://cdn.jsdelivr.net/emojione/assets/png/1f937.png?v=2.2.7"/>
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