Z2 Model number / Fake?

[Lent2019]

I bought a used Z2 (D6503) in case my current one breaks down and I need parts.

I looked at the model number in the phone when buying it and tried a call. It worked.

I bring it home, want to plug it in and I notice the flaps are different?!

What?!

After closer look, I found the SIM card is on the other side.

Screatching my head.....did I get a fake one?

Checking everything I can in the phone, same as mine (except is old).

At the end I put it into a IMEI check, and it came up with a model number L50U . I found it on wiki "May 2, 2014; 5 years ago (China, L50u model exclusively for China Unicom )[2] "

So maybe it's not fake but surely confusing why the other model number is in there. The seller also had no idea and now I have two different models. 

I don't know if anything is interchangable? Including the back cover as it is broken and the picture is bad because of that.

Some pictures in case someone wants to look at it.

[Uliwooly · Accepted solution]

@Lent2019 

that's indeed the Chinese variant, as for spare parts you should be able to use them, of course the housing might be slightly different but battery, cables and camera modules should work. If possible you could return it and get the global version. 

[Lent2019]

Unfortunately the saga continues.

Since the back was broken right at the camera, I finally got it off, the one from my other Z2 didn't fit. See picture.

The other problem is that I can't update it.

While my original Z2 is at 6.0.1    this is  5.0.2  and both Companion and  through the phone, it says software is up to date.

While it would be usable, I would really like to update it.

Any ideas?