and Cooper may not have even worn the tie when the particles were deposited..
I found a 100% gold particle... does that mean he was also a gold miner.
The particles can be from the plane, from handling or storage post Norjak from fingerprint processing,, plus the life of the tie from about 1965 to 1971...
Since the particles are on the backside.. they were deposited from the hands or while not worn.
The particles generally fit pyrotechnics, dentistry, electronics and other environments.
OR a combination of environments.