Leaded Glass Shield (ca. 1920s, 1930s)
A similar shield is described in a 1922 H.G. Fischer & Company catalog as a "Leaded Glass Shield or Cover for the Radiator Type Coolidge Tube—either the 10 or 30 M.A." The device shown here consists of two halves that are attached together with bolts. The flange through which the bolts penetrate has the following text on it: "W. & B. Manufacturing Company, New York. Corning. Made in U.S.A." The glass is completely opaque which would be advantageous in fluoroscopy where stray light would be undesirable.
The tube would be oriented so that the X-ray beam would leave though the circular two inch opening in the shield (facing upwards in the above photo). Note that an enclosed shield like this almost eliminates any loss of heat through the glass, hence the need for some other heat loss mechanism (in this case, the radiator fins).