Wooden backstaff or Davis quadrant made by John Gilbert on Tower, London for Henry Tindall, 26th January, 1759. The navigational instrument is fitted with boxwood circular scales (30°arc 0-25, 60°arc 0-65 & 1’ divisions) on a mahogany frame, a signed inlay wooden plate and decorative stars are stamped on the end of the arcs. The backstaff is incomplete lacking both its vanes.