The symbols for both the evil Decepticons and their opponents, the Autobots, can be seen etched into tram rails in the Kamppi and Kluuvi districts of Helsinki.
Looking like professional work, who engraved them, when and how they got there are still all unanswered questions.
"The logos were etched either at our rail repair shop during milling or else they came that way from the supplier. The work is so finely done that no one did it there on the street," says Helsinki City Transport rail unit director Pekka Sirviö.
The Transformers began as a series of toys that has expanded into a franchise encompassing comic books, animated TV series and films.
Sirviö believes that the logos were put on the tram rails with a humourous intent.
"These arouse mixed thoughts. On the one hand, it's funny, but also a bit weird. Traditionally, what has got etched into tram rails have been dates or years, a sort of signature," Sirviö notes.
More still to be found?
Helsinki takes delivery of track from different suppliers in a number of countries, but most are made in Finland. Helsinki City Transport is unable to say if more may be found.
"We'll see if the Transformers have been around etching more logos, but I can imagine that there are not very many," predicts Sirviö.
Helsinki City Transport hopes, however, that people will not walk the rails in search of more.
"I hope, for safety reasons that the public stays off the tracks and stays on the sidewalks. There is no contest to see who can find the most or where," says Pekka Sirviö.