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Zentmayer's Grand American
binocular microscope

Signed on the foot, J. Zentmayer, Maker, Philadelphia, No. 777. Working height, when erect, 19” to 22 1/2”. Coarse focus by straight toothed rack. Fine focus by short lever on front of binocular tube, operated by a micrometer screw with a large silvered, graduated head. Interocular eyepiece adjustment by racked eye tubes. The massive Y foot supports a rotating base with beveled, silvered degree scale for measuring the angular aperture of objectives. Large turned double pillars and a unique limb with curved triangular opening identify this as Zentmayer’s top-of-the-line stand, built from 1858 to 1876. The goniometer stage has a beveled, silvered degree scale, and rotates on a concentric ring base, adjustable by 3 set screws. The sliding object carriage is held in place by a spring loaded screw with ivory point, and, glides smoothly on 2 rails on the stage plate. The binocular assembly is the Wenham style, with a removable prism housing. The double mirror is 2 1/4” in dia. Most of the original accessories are present, in a fitted drawer. The box is not present. Incl. are 3 Zentmayer objectives (signed only on their brass cases): a reversible 3” & 4” (fits the binocular tube only in the 4” position), 1 1/2” and 8/10”; Bausch & Lomb 4/10” 110° with movable front with scale 0-12; unsigned (J.Grunow?) 1/5”, 110°, with movable front with scale 1-11; C.A. Spencer & Sons 1/2”, 65°; C.A. Spencer & Sons 1/8” immersion, 175°. The 6 Zentmayer eyepieces include 2 matching 5x and 3x, a 15x, and a 5x with Jackson eyepiece micrometer. Accessories include an erector lens (for the monocular drawtube which is not included). A Wollaston camera lucida, achromatic condenser with 2 centering screws and rotating plate of shaped stops, another wheel of circular stops, a brass mounted blue filter, a parabolic illuminator with adjustable central stop. a set of Darker’s selenite disks, a Nicol prism substage polarizer, a Nicol prism analyzer for use between the nosepiece and objective, a parabolic speculum in oval brass box (lid detached), an anamacule cage (only 1 glass disk present), a compressorium (no glass), an exquisite stage mineral holder. The stand and accessories retain most of the original lacquer, with normal wear and scratches. This is the only binocular version of the Grand American we have seen , other than one listed in Billings, but not illustrated.

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