According to Winter Olympic Gold Medals' statistics. Source: Wikipedia, and www.sports-reference.com/olympics/sports/SKJ/
Germany's team in three Winter Olympics, 1956, 1960, and 1964 was called United German Ski Team. Their medals have been put together with the "German team", DDR remaining separate.
Only these 10 countries have won Gold in Ski Jumping, so far - by 2017. Some of these countries' names do not exist any more.