Sure, and thank you, David
The "Ingenieur" was introduced in 1955, was initially given the ref. 666 and has an inhouse movement, developed by Albert Pellaton, the caliber 852X (later, from 1959-, caliber 853X), a wonderful automatic movement with a brequet overcoil and encased under a soft-iron core enabling it to withstand a magnetic field up to 80000 ampere/meter.
This, the Second generation Ingenieur, ref. 866, was produced from 1967 to 1976. The movement was further improved and modified and now named caliber 854X, a movement which is very highly regarded.
The main differences between first and second generation are: The case got bigger, now measuring a good 37 mm w/o crown (1. generations were 36,5mm), and the crown got bigger.
All 2. gen. Ingenieurs have baton hands and a paddle-neck shaped seconds hand (1. gen. were mainly dauphine hands, albeit a few of the late 1. gen. had baton shaped hands too). Hour markers were now all double bar and most dials were given an applied metal IWC logo where most 1. gen. had written "International Watch Co" on it.
This specimen, ref 866 AD (with date), dates to 1970 and has one of the rarest dial variations, the Blue "Soleil" or "Sunray" with 18K white gold aplied hour markers (sigma dial). Most dials were silver and a few anthrazite/grey are known too. It is unpolished and all original. Flawless dial and hands.
I think its a fabolous watch - it has a beautiful, timeless design, a great movement and it wears just wonderfully.
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