The Talking Machine Forum — For All Antique Phonographs & Recordings

Can anyone explain this clamp for an HMV 4 soundbox. It is mounted to an HMV 201 portable.
I'm guessing it is an anti-theft device for an HMV 201 which was on display. The clamp fixes the HMV 4 soundbox to the toneatm so it cannot be removed unless you unscrew it from the clamp. Note the copper lug on the inside of the soundbox between the body and the inside of the diaphragm.

It is indeed a security clip. One is pictured in His Master's Gramophone, page 260, Fig.9.42.