The limbs on a boxlock are far more robust than a sidelock. The sear and bent are at convenient angles and both are strong. There was no intercepting safety on the original A&D design. A number of later variants did include intercepting safeties. Good 'A&W' Webley models with screw grips often had them, for example. You see them incorporated in a lot of nice boxlocks by Army & Navy, William Evans and many others. Plenty of sidelocks don't have them but theoretically warrant them more.

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