This is the traditional “wet fly” hook. Wet flies are time honored, successful, subsurface patterns. (see 1530) These hooks feature a more gradual curve of the wire in the transition from the straight shank to the bottom of the bend.
This shape is associated with an early English hook-maker named Sproat and today is still referred to as a sproat bend. Dedicated fly tiers consider this as the proper bend to give wet flies their aesthetic beauty.