Helmet was made in Brieg / Brzeg (20 kilometers from Wroclaw / Breslau).
This has for sure something to do with the silesian GR11 which garrison was Breslau.
This could be the 1. E.(rsatz Bataillon) G(renadier) 11.
The GR11 had two Ersatz Bataillonen, one in Breslau, the second in Neumarkt / Schlesien (Sroda Slaska)