Here's a new, vintage, product to me. A bag of what I think are stamped (not etched) brass, tension lock couplings.
The mounts suggest 1960's or 70s Hornby replacements, but smaller than the Margate originals.
Assembly is required. Pop the hook assembly into the main part, and push a plastic pivot into place. Ideally, these would be chemically blackend before putting things toghether. A dip in Gun Blue would do the job, if chemicals aimed at modellers weren't available.
Also, why did Cavendish, stick an apostophe in the middle of thier name?