Fugi, can you get a closer look at the helmet for us? It's clearly a Model 1916, but those were used into WW2. They were ultimately replaced by new versions in 1935, 40 and 42 but could still be seen until the end of the war.
It appears that there is a carved in 'helmet decal' below the vent hole. I'd guess it's representing what is seen in this image

This is from the mid 30s.
I've seen a photo of a similar pose but can't for the life of me find it in all the books around me. I'll keep looking. If memory serves the photo was taken at one of the first big public showings of the new German military after Hitler said the heck with the Versailles Treaty limits.
It would make sense that this was commissioned after that and probably inspired by the photo I saw or one similar. That would fit with it being found in the home of some party hack at the end of the war. So figure it's from anywhere from about 1933-37 time frame or so.