FYI.....

Within the last week, I flew a 4 day trip with most of the legs being B757-300 flying. Over those 4 days, we saw 3 different a/c that had the "tag" that you mentioned.

Discussing the topic with a MX guy earlier this week at one of our major out-stations, he said the company (especially MX control) is very aware of this situation. Some CA's have written-up the "tag" as "unauthorized graffiti on exterior of aircraft", thus having to address the issue....sometimes at out-stations which has caused some 'headaches' downline.

The MX gentlemen went on to share that MX Control has been actively tracking the various aircraft in question while attempting to try and 'connect the dots' in solving the mystery.

I'm sure it will just be a matter of time.....