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While it superficially resembles a a more conventional combination dial, the interior workings are quite different: As seen in the first photo below, the fixed outer ring of the combination dial has a group of letters and numbers at the top reading 9876543210abc from left to right. To enter the 4-part alphanumeric combination, one would first turn the pointer to 0, then to one of the numbers 1-9; then repeat for each of the letters a, b, and c (e.g., the combination might be something like 0-8; a-2; b-3; c-5) -- kind of analogous to the operating principle of some modern Fichet Bauche combination locks where you would alternately turn a larger numbered dial marked 1-4 and a smaller dial to a certain number of clicks in between.
The three photos below illustrate different versions of the dial -- the first two (one being the same lock as above from a wider angle) simply unlocked an escutcheon blocking the keyhole for a lever-tumbler lock below the dial and above the handle, such that the combination must be dialed before inserting the key. The version in the third photo (I believe) functioned as a standalone combination lock with a built-in 'T'-handle to retract the boltwork. An all-around interesting combination lock with a user-friendly dialing sequence, although its popularity may ultimately have been limited by the fact that the combination was fixed and could not be changed and also by the limited number of potential combinations (5,040) compared to competing designs.
The escutcheon version, as seen in the additional photos below, operates a sliding steel plate such that in the unlocked position aligns the hole with the keyway, allowing the key to pass into the lock. The second photo below shows the lock from the rear with the mechanism exposed in the unlocked state, with the four sliders aligned, permitting the lever to drop into position. Photos 3 and 4 below, belonging to a different lock of the same model, give a closer view of the locked and unlocked slider positions -- note that here the sliders are actually marked with the combination numbers (0-7, etc.). Photo 5 gives a clearer view of the disassembled sliders (pages 3-5 in the patent above also include diagrams).
Good question on the inner workings, and it's tricky to see from the photos. I don't have one of these on hand to make a video, but I'll come back around and post more details when I have more time later on this evening. I'll also post a full translation of the patent, since that makes the diagrams and the photos easier to interpret.