Karlfonds charity issues.
The Austro-Hungarian empire was ruled by a person (Karl I) who was emperor for Austria and king for Hungary.
Karl I was the last emperor of the Austro-Hungarian double monarchy. He was married with Zita of Bourbon-Parma.
The Karl's Fund is a charity surcharge for Austria.
K und K (Kaiserliche und Königliche) Feldpost = Emperial and Royal field post.
Karlfonds = Karl's Fund.
Karl I of Austria
Zita of Bourbon-Parma