My friend Kuduae gives interesting information…even if they are hints of Germanic tradition.
In fact many systems were designed at the beginning of the last century when it was necessary to install a fragile and little waterproof scope on a quick detachable mount.
In fact, the first H&H Mauser actioned rifles built before 1910 were often equipped with claw mounts and it was not until later that their famous side mount appeared.
Several variations exist and all do not work in the same way.
The definitive mechanism emerged in the thirties and was not equipped with a tension bar.
The tension bar was used from the late seventies and its function is to release the light metal scope tube from of any tension.
I have built several systems of this type which when well executed are very reliable and enjoyable to use.
Of course on the pre war RIGBY we often meet Mauser type quick detachable mounts as manufactured in Oberndorf since it was the Mauser factory that was building the mechanisms for the London Company.
Here are some illustrations of various systems.

DORLEAC
www.dorleac-dorleac.com

Mauser factory mount

H&H first type mount

H&H inverted mount

H&H traditional mount

H&H rail mount

Custom made H&H style mount