This antique brass scientific instrument is an incomplete surveyor’s dial or pelorus, manufactured by the Scottish firm Alex. Mason and Sons of Glasgow. The instrument is constructed from heavy cast and machined brass and features a dual concentric scale arrangement. The outer scale consists of a fixed 360-degree ring graduated in single-degree increments and numbered every ten units. The inner rotating brass plate features two vernier scales graduated from 0 to 60 and is engraved with a prominent N indicating North. The face is clearly engraved with the maker’s name ALEX. MASON and SONS and their location GLASGOW. The reverse side is fitted with a substantial brass mounting arm with pre-drilled screw holes and a central pedestal featuring a ball-and-socket joint, likely intended for mounting on a tripod or gimbal system to allow for levelling. The central plate contains various unoccupied screw holes and apertures where missing components were previously attached.
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