Do you mean the "Vor Gebrauch Sprengkapsel einsetzen" printed on the head of the M1915-M24 grenades? It just says "Insert detonator before use". Depending on year, make and model they usually also have the fuse timer written on the shaft, for example 5½ sek (5,5 seconds), and the manufacturer like AEG or ABB. These days finding one with the stencil intact is very rare and it's usually an indication that it's a reproduction if the stencil is in good condition.