Perhaps they are tables of precomputed inverses of primes to speed up the trial division. There might be up to 100000 entries in the file if this is the case.

Perhaps they are tables of precomputed inverses of primes to speed up the trial division. There might be up to 100000 entries in the file if this is the case. I can't think what else would be in the file. I would have guessed the file was generated by the program and would contain relations from a sieving run for the last large factorisation your uncle did. But I also don't see how these files get generated by the code.