GustafB's comments:
Very interesting photo, these would be French prisoners sone time after 1915 due to the M1915 Bluses worn by the German gaurds. The different cap is a French Bonet du Police, or what we refer to as an overseas, or side cap. It apperas that these French soldiers were captured early in the war, that is to say, before the French swithced over to the Horizon Blue uniforms. I am not sure, but I suspect that the badges/discs on the French POW's caps are their prisoner ID tags. I have on that my great uncle brought home from the camp at Holtzminden, and the dimensions are the same. It is interesting in that Holzminden was the camop where the original "Great Escape" took place, the experiance from this escape was used to make the training manual that taught the boys in WWI who took part in the better know "Great Escap" What is really interesting is that both escapes are so close in the way that they came out, right down to the numbe that escaped, and the number that returned home. The biggest differance was that in WWI, none of the escapees were executed.