The tungsten core is a different colour from the aluminium, and also much harder, so it's easy to scratch aluminium with the tungsten point but almost impossible to mark the tungsten with the edge of the aluminium surround.
@gbj_tester started
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The tungsten core is a different colour from the aluminium, and also much harder, so it's easy to scratch aluminium with the tungsten point but almost impossible to mark the tungsten with the edge of the aluminium surround.