[quirino]

Not OP. It seems they're files which display different contents depending on the program you open them in.

Here's a CCC talk on it: https://media.ccc.de/v/MRMCD2014_-_6008_-_en_-_grossbaustell...

And the slies from the talk: https://www.slideshare.net/ange4771/schizophrenic-files-v2