This is my plate, its for sale.
Do you have any information on it, studio info, C.O.A or receipt?

I'm half way through season three and whenever I see a car I can try and see if I can spot the license plate.
I found this so far:
1. "Cherokee State appears on the license plates on the sitcom Malcolm in the Middle. This is likely intended to be a state nickname."
-wik
2. "In later seasons, license plates display "Cherokee State", which could refer to Oklahoma. In episode 313, Oklahoma Highway Police can be seen on the police car doors. In Seasons 6 and 7, the license plates on the cars are from Oklahoma. This is seen more than once, as in the episode 606, "Hal's Christmas Gift", the license plate on the Mustang Lois is in the parking lot demolition derby with is from Oklahoma, as well as her Tempo. And later, in the episode "Malcolm Defends Reese", Hal's Dodge Spirit has Oklahoma plates."
-yahooanswers.com
3. "In later seasons, license plates display "Cherokee State" which is another name for Oklahoma. Despite that, the look of the plates intentionally made like California's, such as the font of the words "Cherokee State", and digits are in the format of "1 XXX 111", where 1 is a digit, and X is a letter."
-malcolminthemiddle.co.uk
4. "It's difficult to see, but when Lois is in the demolition derby with the other woman, you can just catch a glimpse of the Mustang's license plate. At the top it says "Cherokee State" which is Oklahoma. This could very well be where the family has lived all this time."
-tv.com
Update: Though a hilarious episode, Hal's Christmas Gift, I checked the derby scene but the license plate wasn't in it: