I had noticed that there are horizontal lines of concentrated particles on the tie under UV..
At first I thought they were smears as if an object was wiped across the tie which would be odd.
However, now I think those smears of particles are from the tie clip... the tie was folded over in storage in different ways over the years.. As it was removed it was put back slightly differently..
In other words,, those lines of concentrated particles are from contact with the clasp when the tie was folded up in storage.
The take away... samples were taken from those areas and the particle concentration would be transfer from the tie clasp.
and the clasp was on the right.. (the left side was an error)