How do I find the sub model number on my Z10?

How do I find the sub model number on my Z10?

I know about: Settings -> OS -> STL100-3

I have the limited edition red Z10 (Canada).

Label on the box, or under the battery.

Originally Posted by Phill_UK

Label on the box, or under the battery.

That's what I was told but I don't see RFK121LW or RFF91LW in those places.