Possible Clues:

• Revolver
• Turner producing old rubbish, nothing bishop should collect
• A muscle unaffected by retraction
• It goes round either way
• Turner's rubbish? Yes, possibly
• It goes round and round and round and ...
• Reversible revolver
• Turner anatomical drawing may reveal such muscle
• ___ cuff (group of shoulder muscles)
• Either way it's a revolver