Harrison's 4th Marine Timekeeper Drawing

Plate X, figures 14 & 15 relating to Harrison's 4th marine timekeeper taken from 'The Principles of Mr Harrison's Timekeeper' (1767). Print reads: 'Let the diameter of the upper plate be 1/16 Inch more'. John Harrison's H4 is the most important timekeeper ever made. It also helped solve the Longitude puzzle which helped save countless lives at sea.
Artist: Unknown
Date: 1767
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