You may recall that the addition of silver chain to some designs necessitated that Larkin figure out how to polish said chain-- without it snarling and becoming hopelessly tangled in their tumbler.
They started with a copper cage that allowed them to wrap the chains loose enough to allow the metal shot in the tumbler to work its magic but kept them separated and secure. It worked great-- except the copper did transfer sightly to the silver over time.
So Larkin updated the cage to silver, adding a middle platform to help keep different chains separated and holes in the ends to fasten clasps (they need to polish, too, and picking them out of the metal shot can be time-consuming!).
Larkin loves the process of figuring out exactly what impossibly specialized tools they need... and making them!