Original Item: The Lewis gun featured an adjustable gas system, in which two different gas ports could be selected, L (for large) and S (for small). A lever about 5 inches long was used to rotate the gas regulator 180 degrees to select one port or the other. One end of the lever was machined with a small loop to facilitate grasping, while the other end was machined to be used as a screwdriver for the clamp ring screw. The screwdriver section was normally seated in the gas regulator.

During the First World War, it was decided to give the gas regulator key an additional function: it would be turned into a wrench to unscrew the tiny locating stud inside the clamp ring. This is the same purpose behind the modification of the Lewis spanner. The modification involved two steps: the loop end of the key was machined a little thinner on one side, and the round hole of the loop was filed to produce a 0.25-inch square hole. This square hole became the stud wrench.

We?ve found a few modified keys among our Lewis parts, and are offering both unmodified and modified keys as follows. Note that the unmodified key is itself a basic Lewis gun tool due to the screwdriver feature. This is the modified Key with a square hole.