Don't think they are WW1 Andy. The uniform style, and the fact that they appear to have Kar 98K, and not Mauser 98 rifles, suggests that the pic was taken in the mid 1930s, probably a cadre photo during, or at the end of training
The late WW1 helmets were still in use during this period, and was still in use with some second-line units in the first year or so of WW2, with the 1935 helmet (slightly smaller rim, and no visor lugs) eventually replacing it in front-line, and especially SS units.