Early 1900s W.H. Harling Boxwood Parallel Rule | Navigation & Drafting Instrument

For the navigator … a finely-made traditional pattern parallel rule by W.H. Harling Ltd, of 117 Moorgate, London, dating from the early 1900s.  Crafted in boxwood with raised brass hinges, and measuring 18 inches in length, this well-preserved tool bears the marks of honest use yet remains perfectly functional with a handsome, well-earned patina.  An elegant yet practical instrument, it would make for an intriguing conversation piece on a gentleman’s desk or library shelf.

Parallel rulers like this were indispensable in both navigation and technical drafting, allowing users to plot courses on nautical charts or draw precise parallel lines in engineering and architectural work.  While Harling shifted civilian production to flat-pattern rules after 1929, traditional-pattern models such as this one (with beveled edges and raised hinges) continued in use and were even issued under RAF contract during WWII—often stamped with Air Ministry markings (note: ours is unmarked). 

Founded in 1851, W.H. Harling Ltd became one of London’s foremost makers of drawing and surveying instruments, supplying universities, engineers, and military clients alike. Their traditional-pattern rules represent the firm's early precision work and the lineage of instruments later adopted in wartime service.  The firm merged with Blundell Rules Ltd. In 1961.

Dimensions: 18” x 2-1/2” x 1/4"
Weight: 6.2 oz.

Condition notes: Excellent antique condition overall. Boxwood body is well-preserved, with crisply beveled edges and clear engraved markings throughout, including compass points (NE, SW, etc.) and maker’s stamp reading "W.H. HARLING LTD. 117 MOORGATE LONDON."  Surface displays a few small ink marks, light scratches, and small areas of lightened finish all consistent with age and use.  Brass fittings exhibit light tarnish appropriate to age, all structurally sound and free of distortion. Hinged arms operate smoothly, allowing the ruler to fold and extend without resistance.  See photos for more detail and feel free to contact the shop with any questions prior to purchase.

Unless noted, all items are hand-wrapped and gift-boxed.  We offer flat rate shipping via USPS Ground Advantage for $10, or USPS Priority Mail for $15.  Orders over $100 ship free via USPS Priority Mail.  We pack with safety and care using recycled and recyclable materials whenever possible.