A scarce antique prismatic glass pendant lamp, complete with old brass gallery. American-made, it is a model 2110 'Reflector-Refractor' shade, produced by Holophane in the first quarter of the 20th Century - the design was launched around 1917 in the UK, and was patented in the USA in 1919. We've found an announcement of the 2110 in a Holophane UK booklet that dates to 1917.

From the booklet:

The Reflector-Refractor combines a highly efficient Holophane Reflector (upper section) and a perfectly designed Refractor (lower section). The Reflector gathers from the filament practically all of the available light from an upward direction, and because of the reflecting power of the scientifically designed "stiletto" prisms, throws it downward.

The lamp accepts a B22 Bayonet Cap bulb. It has been fitted with a new English-made lampholder in solid patinated brass and has been fully rewired with a particularly nice Italian-made 3 core cable braided in a complementary variegated grey linen.

The shade is marked: Holophane - Made In USA - Pat. March 1919.