Identify IWC Movement. Need Balance

Hi, I have an IWC Ladies 14k gold watch to service. Having trouble identifying it. It has FHF & 69879, stamped on the top plate, S & CO on the Barrel Bridge, also the number 79 stamped underneath the Balance Cock. I need a balance spring or complete balance.
Has any one got any ideas what calibre this is?
Many thanks
Keith

Dear Keith

What you got is no IWC. Stauffer & Co was a London/La Chaux de Fonds based importer of all kind of watches, amongst others IWC.
You have a FHF, what is another, not that well known brand as IWC is.

Sorry for having no better news.

Regards

Thomas