Household Appliance Spares Matching '9313a Tumble Dryers & Spin Dryers'

There is no picture of the reverse of this knob: but please note there are some knobs which come as two pieces. There is a separate listing of a replacement for just the back (shaft-fitting) part of the two-piece version.
This is a complete one-piece knob which fits directly onto the switch's metal shaft: which itself is a round bar with a single flat side.
This 'pattern' part came with a screw included; but no 'clip': which I assume is necessarily held by the screw: to hold the knob more securely onto the shaft of the switch.
To save waiting for a clip, if it were indeed meant to have been included, I made my own spring-clip out of a brass contact from an old electrical fitting.
In summary, a perfectly serviceable pattern product; assuming you can fashion a spring-clip from somewhere!