The officers strength of the German submarine service according to the Dutch magazine Marineblad dated 1910-1911 no. 11

An item reported that the officers corps of the German submarine service excluded the etat major of the Vulkan consisted of 12 lieutenants 1st class [kapitän-leutnants], 22 lieutenants 2nd class (Oberleutnants zur See} and 17 officers-engineers with the rank of lieutenant 2nd class