Maker

Sokkisha, Tokyo, Japan

Model

OS 1

Serial Number

n/a

Dimensions

45 mm diameter, 100 mm high

Image

Description

This double pentaprism (optical square) allows to set out right angles, to determine a point on a line and to drop a perpendicular from a point onto a line. Points are usually marked by (red-and-white) ranging poles.

The instrument at hand has a window at the top that directs the view to the right, a window at the bottom showing the view to the left and a narrow horizontal window at half height giving the view straight ahead.

The pentaprism shell is made from aluminium and is painted black. A sleeve on the upper part can be rotated to cover the windows of the prisms.

Below the optics is a cylindrical tube (handle) that permits to hold the device or to mount it on a plumbing rod. The plumbing rod, when supported by two fingers, makes the devices vertical. The central bore of the handle has a diameter of 13 mm. The handle has a cut that permits the attachment of a plumbbob.

History & comments

Conservation

in leather pouch 55 x 55 x 112 mm

Condition

some paint damage. Protective sleeve difficult to turn.

Remarks

(Dymo) label 'No. 3" on outside of leather pouch.

Dates

Catalogued by JMR on 9 Oct 2014. Photo by JMR.