As I look at the Lexus website and "Build my Lexus" -- there are 2 (two) character Factory Option (actually Katashiki) and accessory codes that are used to identify the selection. You can see these in the pop-up window when you select the "package" that you want and hover your mouse over the radio selection button at the top of that page.

Is there a comprehensive listing of what these codes describe?

As an example, there seem to be 3 (three) radio options AN, AM and AO ... where is there an explanation of the description for each 2 character code?