Where it comes from
Bending an apple is as old as bending any briar: once stems were vulcanite and shanks could take a curve, factories offered the same round bowl with the bit closer to the bowl so the pipe hung. English and French lists called it a bent apple; Danes later exaggerated the curve. It is not a new shape. It is the apple in a different posture.
The specification
Bowl: the same sphere as a straight apple. Shank: curved, usually a three-quarter or full bend. Stem: follows the curve; often a saddle or a taper cut to the bit. The airway is longer. Weight sits more in the hand than on the teeth. 356/23 is the bent apple in this cabinet: art-rusticated double wall, navy lattice cage, Cumberland stem, engraved silver band. No millimetre card on that plate.
Next to a half-bent
392/24 is filed as a half-bent apple — less curve, still a round bowl. 356/23 leans further. If you want the apple and less weight on the teeth, these two are the comparison, not the straight 423/24.