German Type UB III submarine
SM UB-110 was a German Type UB III submarine or U-boat in the German Imperial Navy during World War I. Wikipedia
Launched: September 1, 1917
Part of: Flanders U-boat flotillas
Commanders: : Kptlt. Werner Fürbringer; 23 March – 19 July 1918;
Test depth: 50 m (160 ft)
I can’t see any signs for what all the valves do, would a crewman just have to know by heart what they were all for?