I have several Shimano qr skewers gathered over the years. Some have a flat-head screw that can be removed to remove the cam lever, others have an E-clip holding the lever in place and some are "blind" and there is no apparent way to disassemble them. I also have a pair of Campy skewers and they have an E-clip retaining the cam lever. There is no obvious pattern to age or component family.