Nexus S version confusion

[Guest vkashin]

Hi.. i've recently bought a Samsung Nexus S online, which i believe to be a recond set..

attached along with this post is a photo of the bootloader screen..

my question is, what does it mean by carrier info : STK?

the sticker at the battery bay says GT-i9020, but a search of the IMEI shows that it actually is a GT-M200, a south korean set instead. so what firmware should i flash?

this is because the phone does not recognize my SIM card at all, and i have tried flashing both SOJU and SOJUK factory firmware images, especially the radio part, but still i'm unable to get the phone to recognize my SIM card.. help please..?