That's cause you have the earlier version of the shutter possibly late 1940's to early 1950's vintage.
The face plate is retained by the circular device with two small holes and a flat edge in it just below the index marker. Turn the retainer until the flat is against the center of the shutter then turn the faceplate counter clockwise until the ears on it align with the slots in the center of the shutter housing then lift the plate straight up. Do not remove the speed ring or hold the shutter by it. There are several pins and levers that must fit into slots in the speed dial which can be confusing for an inexperienced person. Just turn the face plate to the remove position and check the shutter operation. The face plate should turn easily. If the shutter works correctly with the face plate loose or if the face plate is difficult to turn then something is bent. A .001 bend on the speed dial can affect shutter operation. Everything is a snug, machined fit with no play so it is easy to slightly bend the speed dial during assembly.

The shutter will be very similar to the manual reference one with only minor differences so it can be used as a guide for parts positioning and adjustments.
I'll leave it to you to decide whether to proceed, return, or take it to a repair shop.