There are three versions of the German Flying Pikachu:
- Fliegendes Pikachu with Pikachu Golf stamp of the Australian Pikachu World Collection 2000 set
- Fliegendes Pikachu without the stamp. Basically just the regular released German Flying Pikachu
- As mentioned by @muk , the Flug-Pikachu. This one was very short-printed. The reason there are two is due to the WotC to Nintendo transition. This is also the reason there are two Surfing Pikachus in French (although both aren’t too hard to find).
Most promos printed in the Nintendo era are way rarer than the one of the WotC era however. The German Flug-Pikachu I’ve only seen once, which is the copy you can find here on the forum of @omahanime . The Spanish Flying and Surfing Pikachus, and German Surfing and Birthday Pikachu (all printed after Nintendo took over) are equally as rare. All five of these cards are the only WotC Pikachu promos I’m still missing, so if anyone has one of these, I don’t mind paying 200 USD each (and 800 for the German Birthday Pikachu).
The first two Fliegendes Pikachus can be found everywhere. The one you have I see for sale all the time at pokemoncardmarket. The Flug-Pikachu on the other hand, nowhere to be found… 
EDIT May 2021: Removed some of the information above, since it was incorrect. Nintendo didn’t took over until 2003, even though these promos were already printed in 2000/2001. I’m not sure why some are lacking the Wizards in the copyright information and others not, though. All I know is that most foreign promos that are missing the Wizards in the copyright information are very hard to find…
Greetz,
Quuador