Welcome to the club.
The Model 555 is essentially the Model 550 with a detachable, 3 round, single-stack box magazine. Not too common, but not rare. The ones I have seen are usually in the Lux stock configuration. If you search on "CZ 550" you will find lots of information.
You will find that the Lux stock is perfect for shooting iron sights. Not so much for shooting with scopes - it is hard to get a consistent cheek weld for scope sighting with the Euro-humpback stock. Still, a lot of people make it work.
Since your gun is new, I recommend working the action a few hundred times to smooth it up. My 550 was a little rough at first. Also, try the set trigger at the range and get a good feel for it before trying it in the field. I love the set trigger on mine, but it is awful light until you get used to it.
Please post pictures when you can, especially of the magazine. I am willing to bet that many on this board have never seen a 555.