In 1875, Westley Richards started building side-by-side shotguns on their famous Anson & Deeley boxlock action. Twenty-one year later, the company updated the A & D design with the famous Detachable Lock Action. Check out the pics below to see some of what sets these designs apart.
This first pic shows a regular Westley Richards Anson & Deeley boxlock action. Note the three pins on the side of the action. Those pins fasten the lockwork in place.
The next pic shows a Westley Richards droplock. See how the the three pins on those three pins are missing on this gun? That’s because the detachable lockwork on this Westley is fastened on plates housed inside the action.
Here’s another pic of a standard Westley boxlock. Even though this shotgun is equipped with a hinged floor plate, it’s a fixed-lock gun.
This is a droplock with the floorplate removed and the left-had lock lifted from the action. See the plate to the back of the lock? That’s what the lockwork is mounted on.
In this final pic you can see the set of the locks dropped all the way out of the gun. You can also the plate that entire lock mechanism is mounted on.