Most nations’ armed services past, present and likely future, the most junior enlisted grades often require little more than the requisite Time-in-Service (TIS) and Time-in-Grade (TIG), to use contemporary US military vernacular, to be promoted.
Germany’s armed forces were no different in promoting their junior enlisted. The pictured rank, Oberschütze (Obergrenadier, ~kanonier, etc.), Senior Private or Private First Class, was reintroduced as the ranks of the newly created Wehrmacht exploded, as the organization emerged from the 100,000 man Reichswehr.
Oberschütze was instituted for those that met TIS and TIG requirements for the automatic promotion from Schütze to Gefreiter, but weren’t quite ready for the additional responsibility or needed additional time to master competencies in their career field and basic soldiering.
The nickname for the rank was “Dippen Stern”, or Idiot Star. Self explanatory.
After four months of satisfactory active service in a combat unit and a total active military service of 6 months the Oberschütze was eligible to be promoted to Gefreiter.
Likewise, the rank/position of Stabsgefreiter (Staff Corporal) was for those that have maxed out their TIG but were not promotable to the NCO grades–being a career lasting rank. The rank was discontinued in 1934 but reintroduced in 1942, becoming promotable to the NCO grades.
Rank images courtesy of Wikipedia.