Coated metal. It's worth putting a scrap of leather over the spinner.
..which brings us back to the hide hammer.
Why did they invent 2-eared spinners in the first place? So you could knock them on and off with a hammer. So what on earth is wrong with using a good old Thor No 2?
- Heavy enough to do the job easily
- leather faced so you won't mess up the spinner
- cheap as chips (£25) even if you don't replace the leather section when it wears and buy a whole new hammer instead
- British made
- the right tool for the job.
All the other solutions in search of a problem seem to be directed at relieving gullible owners of their money.