Originally Posted by Parabola
The Piani Fissi seems to be a somewhat simplified version of the Bonehill Patent Clip Lump of 1884.

In my Bonehill Belmont Interchangeable Hammerless, an early machine made gun, the clip lump incorporates not only the lump and barrel flats but also the top extension, lower rear rib and forend loop.

Thanks for the info.
Learned something today.

Upland, grouse, woodcock