STONE!!! YOU SAID (and you err): "The speed loss is often in the exposure level, so if the film was already previously exposed he wouldn't be losing any more speed"
WRONG! Let me remind all, including Stone, that, true, the exposure was proper AT THE TIME. But with decades passed, THAT exposure is NOW GROSSLY INSUFFICIENT. The film has steadily been losing speed through the decades, INCLUDING THAT WHICH RECEIVED SUCH ANCIENT EXPOSURE. The ONLY way to ATTEMPT to resurrect it is to give a LOT of development in order to get WHAT REMAINS out of the waning, feeble, age-agonized, incapable-of-self-sustainment, halides! - David Lyga