My father had similar lead soldier molds for WW-I, we still have the molds, they include riflemen, Machine gunner's, etc. But more importantly, the lead that was often used was NOT soft plumber's lead, Plumber's lead will not take a sharp impression in the mold and much of the detail would be lost using it. Instead my father and many others used an alloy of lead known as 'type metal' It is an alloy of lead, tin and antimony. It has a particular property of expanding just prior to solidification thus getting a very sharp image, it is also harder and more brittle than pure lead. The sharp impression is particularly important for it's original use as Printing type, and for use in the Lineotype casting machines that cast a full line of letters rather than having to place each letter by hand in making up a line for the printing press. I believe that your soldiers may be cast from the 'type metal' alloy of lead
