IWC Watches with Guillaume Balances?

In 1899, Charles Édouard Guillaume invented a variation on the traditional
brass and steel compensation balance. He replaced the steel inner lamina with
a nickel steel alloy, eliminating the middle-temperature error. These were
called "Guillaume balances", "Integral balances", or sometimes "Crausaz
balances" after a balance maker who copied the invention without mentioning
Guillaume's name, or sometimes very incorrectly "Invar balances" (incorrect
because there is no Invar in the balance). Versions of Guillaume balances were
made for box (marine) chronometers and for watches.

Did IWC use Guillaume balances or their equivalents in any watches?

Regards, David
Eur Ing David Boettcher FBHI
www.VintageWatchstraps.com

Dear David

some of the "Quality Extra" pocket watches have a Guillaume balance. More or
less all have been observatory ratings been awarded.

Regards

Thomas Koenig

Dear Thomas,

Thank you for your reply, that makes a lot of sense. Guillaume balances were
expensive and only really showed in observatory trials, in everyday use their
benefit would have not been evident due to all the random shocks and position
changes that a watch experienced.

Do you have any more details of the "Quality Extra" pocket watches?

Kind regards, David
Eur Ing David Boettcher FBHI

Dear David

In case you can understand an German language article: I wrote an article on
the Quality Extra pocket watches some years ago in the German watch
journal Klassik Uhren.

Regards

Thomas

Dear Thomas,

I am not fluent in German (my grandfather was German but my father learned
only English) but I understand enough to be able to read articles about
watches, I would be very interested to see your article.

Regards, David
Eur Ing David Boettcher FBHI