The IWC Ingenieur was introduced in 1955, featuring the calibers 852 (time only) and 8521 (date), a new winding system developed by Albert Pellaton. It was an anti-magnetic wristwatch with a soft iron inner-case and dial.
The first generation of ref. 666A Ingenieurs was produced in a variety of dial styles and in both stainless steel and 18k gold, and are sought after by collectors.
The present example features unusual and much rarer 18kt gold case, giving the watch a more "dressy" feel.