Frohike : [examining a used envelope] I got something here. Writing. Somebody wrote on top of the package and left an impression.
Ringo Langly : Your sci-crime guys at the Bureau have a laser that can measure any change in a surface down to a few nano-meters.
Byers : Actually, they can lift a perfect impression using magnetic toner and a sheet of Mylar.
Frohike : Actually...
[while they have been debating, Mulder has used a pencil to make a rubbing of the impression on the envelope]
Mulder : Actually, it's a phone number, New York City area code.
[hands Frohike the pencil]
Mulder : Now don't drop that. That's a finely calibrated piece of investigative equipment. I gotta make a phone call.
Frohike : [looking at the pencil] I'll be damned.