Marcel pl. Kiepach (1894-1915) was probably the youngest inventor that Croatia ever had. He patented his first inventions in several European countries already at the age of 16, mostly in the field of electrical engineering. His inventions have been patented in France, Germany, England, Switzeralnd and in the USA.

Photo from www.krizevci.eu

His first invention (maritime gyrocompass, which shows the North irresepctive of surrounding metal objects or the influence of magnetic forces) was patented in 1916 in Berlin (Kaiseriches Patentamt) under No 246656, owner Marcel von Kiepach in Križevci, Kroatien.

Source genius-croatia.com

The same invention was patented in London already in 1911, under No 28696, owner Marcel de Kiepach, Theaterplatz (Kazališni trg) broj 8, Zagreb, Croatia, Austria, Landowner. In 1912, he patented his dynamo machine for vehicle lighting in Paris. Even today we can see his invention being used on bicycles.

Photo from www.krizevci.eu

Marcel died very young at the age of 21 as a volonteer in Poland in 1915 during the First World War. An extensive documentation about him and his patents can be seen in the City Museum of his native town of Krizevci. Today, the town of Križevci has the street named after him and the Marcel Kiepach Innovation Society.
 
en.wikipedia.org/wiki/Marcel_Kiepach
hr.wikipedia.org/wiki/Marcel_Kiepach
prigorski.hr/marcel-kiepach-krizevci-12-veljace-1894-ruska-poljana-13-kolovoza-1915/
Zoran Homen: ZABORAVLJENI IZUMITELJ NA POLJU ELEKTROTEHNIKE [PDF]