I think our memory of how fine grained it was is colored by comparison to the faster films of its day. It was considerably finer than medium speed films, Plus-X and Ilford FP[whichever] of the day, and far finer grained than the Tri-X/HP[whichever] of its day. But those films have been continuously improved ever since, not to mention we have various new tech films now to compare it to.