I have a Boeker Speedlock. It has a coil spring. Itīs slightly slower than the knives with leave spring. It has two major advantages though. The coil spring is less prone to breakage and it has enough travel to open the blade if it was stopped on the way. Due to the mechanism it can be closed with one hand.
Iīm satisfied with my Speedlock.
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If it isnīt broken, it doesnīt have enough features yet.