But this one is completely new to me. I speak German and know what Sternzeit Reguliert means and what it is but can you enlighten me about the reason behind this rare regulation and eventually where (what units) that used it? The only reason I could think...
The watches showing sideral time were used by artillery to determine true (not magnetic) north together with a theodolite. To launch projectiles that are supposed to hit targets over the horizon you need to establish both a horizontal and a vertical plane...