Generation of IWCs. Especially the 85xx movements.
I have a Yacht Club with the 8541B and I absolutely love it for:
Being most reliable and accurate
Being such an efficient autowinder
Its soft and crisp manual winding
Having absolutely NO slack when adjusting/setting time
...and much more
And that's a YC - the Ingenieur has all that history and aura to add.
Congrats with this new Inge - it's a treasure
Best regards
Nikolaj