It's a knob. I like it better than the original.
I printed it with the logo down and the "Octagram Spiral" for bottom layer to make a cool effect.
NOTE: This is my model and original design, as is the same posting on Thingiverse, however, Thingiverse has not been able to help me reset my account after multiple attempts so I am importing everything manually to Printables.
The author marked this model as their own original creation.