The S-mine explosive content was either a wax filling or it could be filled with granuals depending on year etc. The section containing the explosive on some mines had spaces s similar to a normal charge. I would take a very very small piece from your what looks like a charge and check to see if its bitchimum but i don't think so, it looks as if your charge has dried out and shrunk into 3 chuncks as it looks if there would be a space on the outside, if the charge touched the centre flash tube. It would unlikely be Nipolit as this stuff i belive can be machined to shape but not sure, if it can be then it would have to be very tough (for machining) otherwise it would crumble to bits but you never know what they did during the war. Some S-mine fillings when dismantled, the charge came out as a block that could be removed as one piece. I belive that these late war mines had a white band around them, maybe its was an early batch where they just put a white stripe on to start and though it would be better to put it all around to be better visualy, As for casting the sections to copy i would use a silicone moulding material and use coloured plaster of paris. Nice to see the wax paper and a very nice condition mine.