Those two rifles were definitely marked using different roll stamps. That is not uncommon with mass production, since roll stamps are often worn, broken, or otherwise become unusable after a time. Usage can range from as few as 2000 impressions to many times that depending on the material of the stamp, how much pressure needs to be applied, and the hardness of the material being stamped. Rifle receiver rings were normally rolled against a semi-circular stamp, both the receiver and the stamp moving to prevent slippage.
Generally, in mass production, when a marking was decided on, a master die was made by hand, by a person called (in English) a die sinker, using hand stamps for letters and numbers and engraving symbols as needed. That die was not reversed; it looked like the finished product would look, but was flat. From that, a number of master stamps were made, and those were used to make working dies from which the round working stamps were made. When all the working stamps wore out or broke, new ones were made from the working dies, and so on. Only when the master die became worn out, unusable, or outdated (e.g., change of company name) would a new master die with possibly a different type font or size be used to make up a new master die.
Obviously, the more impressions that had to be made, the faster the whole die/stamp chain became unusable, and it certainly stands to reason that in 1917, Mauser receiver ring stamps were making a lot of impressions.
There might even have been several master dies made earlier, but if the hand stamps used the same font, it would take a detailed examination of many rifles to find the change points.
Jim