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[[encircled 120]]
[[double line frame around illustration]]

[[image: top view of a circular brass circle dial with a moveable arm with a moveable steel scribing arm attached, mounted on an adjustable steel base with a thumbscrew.  The dial has four concentric circles of holes or depressions around its outer edge.  The outer circle has eight holes; the next circle has ~ 152 holes; the next 16; the inner circle ~ 112 (unequal per quadrants, hard to see, probably schematic rather than accurate count.  Since the  third ring (16) matches the points of the compass (N, NNE, NE, ENE, E, etc.) total holes are probably 360 as in 360°, and if the device is connected with a sighting device (transit), when the transit is on target the pin in the scribe arm is in one of the holes or depressions, it would give the direction of the target, i.e. as positioned in the drawing about 5° E of N]]

[[center image: bottom view of the device showing the lateral screw adjustment turn-screw and lock. As drawn, as the turn-screw is turned the upper dial would move laterally back and forth across the base

[[small image right]] locking clamp for turn-screw]]

[[bottom image: side view of the device showing the threaded center arbor and a projection from the scribing arm down to the surface of the dial.]]

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Transcription Notes:
mandc: pure guess as some type of range or azimuth measuring or pointing device due to likely aiming at point of the compass.