Since the Titanium particle narrows down the suspect list so dramatically it makes sense to assume the tie did belong to DBC. A second hand purchase only opens up a whole new can of worms.
The second hand store theory is much like the plant theory. It is used mainly by those who have a suspect theory that benefits from it.
But, the titanium had to come from somewhere. Even if the tie was bought at a second hand store, the titanium if that rare, should narrow the location of such a store. Thus, it would narrow the location of our guy.
Either the tie was DBC's and the Titanium is as important as the Tina Bar money or he bought it second hand in which case it's almost useless. If I lived in the area i would be trying to get my hands on employee lists from the handful of companies that could be the source of the particle. That's a game changer. On the other hand, if it came from a thrift shop it doesn't help much at all as it puts too many variables into the equation.
Boeing made massive layoffs in the spring of 1971 after the government halted funding for the Supersonic Transport project. Thousands of employees lost their jobs. Many of those employees would have been engineers and supervisors (the tie-wearing types). And titanium was used for the aircraft (in fact, the halting of the project had a major impact on the price of titanium immediately following).
So there's Boeing (located in Seattle). There's titanium. There's guys who wore ties around that titanium getting laid off. The government was to blame. Six months later a Boeing airplane is hijacked in the same area, the government is ransomed and a tie with titanium particles is left behind. Circumstantial or not, it's pretty damning.
It's a pretty good bet that tie came from a Boeing worker, whether it actually belonged to Cooper or was bought second-hand.
