Notice that the rifles on the card are the early gas traps with slant cut op rods, flush nut sights, and grooved lower bands.
That is most interesting! I hadn't heard of these cards before, so thanks for posting the pics and info about them. As you pointed out, those M1's are the earliest ones so the cards likely were produced before WW2. Nice attention to detail in the cards, and it's interesting the soldiers are wearing the M1917 helmet - and are shooting the rifles with their thumbs on the same side of the stock as their fingers