yes, when I was in the French army a few (!) years ago they were called "pain de guerre" ("war bread") but the old French hard tacks were harder than anything I've eaten in my life!
Once, I've put a piece of the old "pain de guerre" in my mouth at 8 AM, I've kept it there just like a tobacco quid until 11AM before it started to melt
Generally, I used to bring it home for my rabbits or to give the full box to a farmer for his pigs and get some milk or eggs as a counterpart
Now, the biscuits in the RCIR are very similar to those in the other
European rations.
The Hartkeks are not bad (including the 1980’s ones that I remember) but my favorites are the "Brown Biscuits" in the British packs.