This is a bobbin to wind yarn (wool) onto using an Empisal Knitmaster Wool Winder. The printed bobbin has a couple of small holes in it to fix the yarn at the start of the winding operation. Some interior bumps catch the splines on the winder to stop any slippage while winding.
I've been printing these with PETG rather than PLA as it's less likely to shatter when dropped.
Print with the solid face down.
I've included the OpenSCAD files if anyone wants to tinker.
The author marked this model as their own original creation.