Both Rolex and IWC saw the need for a watch for engineers and scientists in the 1950s, combining rugged automatic movements, water-resistant cases, and anti-magnetic concepts in the Rolex Milgauss and this IWC Ingenieur. The concept has remained for over 50 years, with the IWC Ingenieur family spawning many models, including an iconic redesign by famed designer Gerald Genta, a pivot to motor racing, and the use of exotic materials like titanium and ceramic.
The Ingenieur had become somewhat stale by the mid 1970s but famed designer Gerald Genta had shown a stylistic path forward with his groundbreaking Audemars Piguet Royal Oak in 1972. Genta designed three “SL” or “Steel Line” watches for IWC, of which only the Ingenieur was presented for sale. The production “Ingenieur SL”, introduced in 1976. Like the Royal Oak, Patek Philippe Nautilus, and Vacheron Constantin 222, the new Ingenieur SL had a “sandwich” case, with both the caseback and bezel being removable. Measuring 40 mm by 38 mm around a 30 mm dial, the “Jumbo” nickname seemed appropriate for the time. Poor sales spurred IWC to search for a smaller and thinner movement to allow the watch to be reduced in size to 34 mm for the 1980s, with most sales focused on the "Skinny" Ref. 3305 and 3505/3506 quartz and automatic offerings.
Like most watchmakers, IWC lacked an in-house movement coming out of the quartz crisis and had turned to ETA to supply a suitably small and slim movement for the “Skinny” Ingenieurs. The company had developed anti-magnetic variants of ETA movements for Porsche Design (Cal. 37541) and the Bundeswehr (Cal. 3755AM) and wanted to apply this know-how to their signature engeineer watch. The result was this Ref. 3508, dubbed “500,000 A/m” thanks to the remarkable performance of IWC's new Cal. 37590. Unlike previous Ingenieurs, Ref. 3508 needed no soft iron inner case to resist magnetism The movement used a special hairspring made of niobium-zirconium, anti-magnetic escape wheel and pallet fork, and rotor bearings made of ruby.
Although a tour-de-force for the company's engineering department, the Ingenieur “500,000 A/m” proved to have serious issues with isochronism in real-world use. Temperature changes in particular caused havoc for the niobium-zirconium balance spring, causing the watch to gain or lose time. IWC attempted to address this with careful selection of springs but it was no use The technology just wasn't ready for the market. After selling just a few thousand examples, IWC retired the watch from the market in late 1992. It was replaced by the conventional "Officially Certified Chronometer" Ref. 3521 with a Jaeger-LeCoultre-sourced movement.
The Ingenieur “500,000 A/m” strongly resembled the preceding Ref. 3506 "Skinny" Ingenieur SL Automatic, with the same size case and similar styling touches. Like the original Ref. 1832 Ingenieur SL from 1976, it featured a tripartite case with a screw-down bezel much like a traditional waterproof caseback. The tonneau case also resembled Genta's Ref. 1832, with an integrated bracelet or optional crocodile leather strap.
The “500,000 A/m” Ingenieur was available in steel or gold filled with or without a bracelet (Ref. 3508 and 3518, respectively), in solid 18 karat yellow gold (Ref. 9238) or gold with a diamond bezel (Ref. 9258). Sales were poor, and the "Officially Certified Chronometer" Ref. 3521 took its place in 1993.
The Ingenieur range was much more limited in the 1990s, with just the three-handed Ref. 3508 or "Officially Certified Chronometer" Ref. 3521, the Ref. 3733 Chronograph or Ref. 3805 Chrono Alarm, and the short-lived Ref. 3540 Perpetual Calendar.