Pair of Parallel Rolling Rules with Carrying Cases

Pair of mid-20th century parallel rules; one W.H. Harling (London-based drawing instrument manufacturer), boxwood & lacquered brass parallel rule for navigational use, includes a fitted mahogany box with printed deviation table inside, circa 1930’s, rule measures 15” x 2.75” inside a wooden carrying case that measures 16” x 3.75” x 1.5"; one marine brass parallel rolling rule in wooden box labeled 'Patt. 160100,' originally used for marine navigation, ruler measures 18.5" x 2.5" inside a wooden box measuring 19" x 4.75" x 1.75".
Condition Report: Both rules in good condition, both cases in good functional condition apart from numerous scratches and chips