Was the spar material DTD 683. The stress office where I worked had a chunk that had not been anywhere near an aircraft, but had turned into a all by itself purely on age.
Mind you, I have seen (long time ago now) a trailing spar of a Boeing 720B in a similar "crumbling cheese like mess", quite a sobering event given I had arrived at the maintenance base on that particular aircraft only the previous day. Granted the aircraft had quite some hours accrued, even so, sobering ! I took small package of the crumbs back with me to home base; more than a few of the people there first thought I was having them on !