Hello!
It's a lid for the DF64's grinder dosing cup.
I have quickly made this after seeing Lance Hedrick's recent video about WDT tools. It is made so that it's tight and the coffee grounds can't get out when shaking it and distributing the coffee grounds before dosing in the portafilter.
If you want I can make it looser.
If you have any idea of how to make it better write a comment and I will try it.
Update V2 :