| DESCRIPTION | HISTORY |
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This instrument, which is much larger than the other earlier example in this collection, is still relatively small. It stands about three inches high in the mid position. The lens casing diameter is about 1 3/4 inches (31 mm) in diameter. Two major optical elements are separated by about 1/2 inches (5 mm) in air. The two sets of legs, operating in pairs can be moved apart or together to focus the instrument as moving them apart lowers it and moving them closer to each other raises it. In working position, the optical elements can be tilted in either direction to extend the field of vision without moving the instrument or changing its focus; this instrument is missing its top cross-brace which makes tilting it in either direction possible. It may be that a previous owner removed that piece for that very reason. The opening of each side is limited by a slotted curved piece which serves to keep the instrument symmetrical. All the fasteners are rivets, there are no screws; this makes the adjustment liable to wear over time with no easy recourse to tighten it. The patent date is embossed into the inside of one leg: 'PAT. DEC 25 77.' This inscription is worded identically to the inscription on the smaller model. Another difference between this and the smaller example is the focal length is much longer on this larger model.