HSTE[Omega Moderator]
4530
Four generations of IWC Ingenieur. From left to right:
The ref. 666, the ref. 866 (special version: believed to have been a "military dial" prototype), the ref. 1832 "Jumbo" and the ref. 3508 (special version: 500'000 A/m).
Cheers, HSTE