It's an ABUS? Do a search for "security pins", "spool pins", "ABUS"...
Not necessarily in that order though... try a search for "ABUS" first.
(If you are not sure why I say this, then do a search for the word "search".)
I am not familiar with that particular model, but it almost definitely has security pins of some sort. Spools or mushrooms, or something...
Only 3 pins? Wow!

I am going to have to search for info about that one myself too.

Did it come that way, or did someone take some pins out?
What you are describing is not wierd for an ABUS.
Anyway, to help you out just a bit, the fact that you mention that pushing some pins turns the plug backwards suggests spool or mushroom pins. If you are impatient and just wanna pick, since you have gotten that far....
try this! Get it stuck where the plug will turn slightly. Push on a pin that "pushes back" and let it push back as you balance the tension just a bit. slowly keep pushin the pin until you feel a nice click! Repeat this for any other pins that feel the same way, but leave the pins that don't push back as they are. There is a good possibility the lock will open if you do this carefully. If not, do some reading or try again and then do some reading!
But don't forget to search and read as much as you can before posting something that may be covered already! I gaurantee a search will turn up lots of info to help you! Good luck and have fun with that 3-pin ABUS! It sounds like an excellent lock to learn security pins with.