Good evening. Unfortunately I haven't recorded information sources (it was a few years ago), but there was also information that only the first part about 20 000 pieces was stamps with application/addition specifically of iron from the tank, but because of difficulties of stamping of such alloy subsequently only copper, nickel, etc. from this tank were added to alloy. It is also visible on structure and quality of medals. This question can probably be clarified by colleagues from South Africa, if they are here …