These days the Hanoverian mouthpiece is usually found on a pelham bit or occasionally on a snaffle
It has a large central port with rollers on each side. The rollers are supposed to encourage the horse to relax its jaw, although some say that their function is to prevent the horse grabbing the bit or leaning. The sides of the port can be fixed or hinged – the latter producing a more severe “nutcracker” action.
The mouthpiece of the original Hanoverian bit shared all these features, but formed part of a lightweight curb bit.
The curved cheeks of the bit certainly appear German. It could have originated in Hanover, but the name may just refer to the Hanoverian monarchs who ruled Britain for much of the 18th and all of the 19th centuries.
Unfortunately I do not speak German but I have found references in Franz von Miller’s 1788 work on infantry & cavalry equipment to a “walzenmundstück” which I believe is a mouthpiece with rollers.
The design had certainly found popularity by the mid 19th century : In J.S.Rarey’s 1859 “The Art of Taming Horses” he describes “A powerful variation of the Pelham, called the Hanoverian has within the last few years come very much into use. It requires the light hands of a practised horseman to use the curb-reins of a Hanoverian on a delicate-mouthed horse; but when properly used no bit makes a horse bend and display himself more handsomely, and in the hunting-field it will hold a horse when nothing else will…”
Of course I started looking into the history of this bit because I found an example :
It is stamped on both cheeks “Worsley” . I had never heard of this maker or retailer but some more research found a P.Worsley, Saddler & Harness Maker at 57, South Audley Street, London in the 1814 Post Office Directory. His will, dated 1838 is in the National Archives. His son Peter Owen Worsley took over the business, the last reference I can find to him is the Post Office Directory of 1843. So no exact date but probably first half of the 19th century
And I find myself wondering what the Germans call it ?