Air carrier Captain commuting in jump seat reported an NMAC during cruise flight with a UAS. No evasive action was taken.

Narrative

I was commuting in the jump seat on flight ABC ZZZ1 to Newark on Day 0. Our route was the ZZZZZ.ZZZZZ1.FLOSI4. Approximately 26 minutes (XA10Z) into flight and at an altitude of 12;000 feet and 250 knots; the First Officer pointed out what he first thought was a bird at roughly 1 o'clock and low. The Captain said he could see it. I picked it up through the ride side window as it passed in a parallel track forward to aft of our flight track. We all agreed it was a drone. The drone was white and black in a triangular configuration. I could clearly identify specific markings on the black parts that had white hash like markings on it. Because of the specific markings I picked up; I would say the drone was significantly inside of 500 feet and approximately 1.5 to 2 meters in diameter. If the drone was actually smaller than it appeared than it was even closer. It passed under the right wing. Since we were traveling at 250 knots I don't think it is possible to determine whether the drone was traveling in the same or opposite direction as we were. All I can say is that it did not appear to be crossing our path. I believe this drone posed a potentially significant threat.