The Future Gadget 204, 2nd Edition Ver. 2.31 (FG204 for short) from Steins;Gate, is the Time Leap Machine used by Suzuha Amane to travel back in time. Of which it was a successor to the Phone Microwave [​Subject name to change]

The ones who built it may vary from timelines, depending on the circumstances. Same as with it's name

Personal Note: Happy Holidays!... And SERN is after me, El. Psy. Congroo. (Insert menacing laugh etc. Mad Scientist)

Also, I am not joking with the name, it's the actual name given from the VN/Anime.