How to know which version my Galaxy Nexus is

If you go to your settings menu, then at the bottom "About Phone" you can look for information in your device that matches below. Look to the software build sections.

Device: maguro, Board: tuna

16GB, GSM 850/900/1800/1900, UMTS 850/900/1700/1900/2100, HSPA+

Configurations:

yakju
Model: GT-I9250

Worldwide, not carrier-specific, Google-branded, supported by AOSP

Software builds:

ICL23D, ITL41D, ITL41F

Radio builds:

I9250XXKK1, I9250XXKK2, I9250XXKK6

yakjuxw
Model: GT-I9250

Austria, Belgium, France, Germany, Hungary, Italy, Spain, UK, not carrier-specific, Samsung-branded, not supported by AOSP

Software builds:

ITL41D-I9250XWKK5, ITL41F-I9250XWKK8, ITL41F-I9250XWKK9: supports additional locales

Radio builds:

I9250XXKK1

yakjuux
Model: GT-I9250

Canada, Bell Canada/Virgin, Samsung-branded, not supported by AOSP

Software builds:

ITL41D-I9250UGKK7, ITL41F-I9250UGKL1

Radio builds:

I9250UGKK7, I9250UGKL1

yakjudv
Model: GT-I9250T

Australia, Telstra, Samsung-branded, not supported by AOSP

Software builds:

ITL41F.I9250TDVKKB

Radio builds:

I9250TDVKKB

unknown
Model: GT-I9250M

yakjukr
Model: SCH-M420S

South Korea, SK Telecom, Samsung-branded, not supported by AOSP

Model: SCH-M420K

South Korea, KT, Samsung-branded, not supported by AOSP

yakjusc
Model: SC-04D

Japan, NTT DoCoMo, Samsung-branded, not supported by AOSP

Software builds:

ITL41D-SC04D0MKKD: no tethering support

Radio builds:

SC04DOMKKD

Device: toro, Board: tuna

32GB, CDMA2000 800/1900, CDMA2000 1xEV-DO Rev. A 800/1900, LTE 700

Configurations:

mysid
Model: SCH-I515

US, Verizon, Google-branded, supported by AOSP

Software builds:

IFL10B, IFL10C, ITL41D, ICL53F

Radio builds (CDMA / LTE):

I515.09 V.EK01 / I515.EK02
I515.09 V.EK05 / I515.EK02