Curiosity got the better of me, I went back in to my A20 to see if I could find that thing. There it was, just inside the back cover, not at all buried deep in the guts of the radio like the button cell is. I have no idea how you even got it out, and you are right, the part number spec is not visible, I was sorta hoping I might be able to see what it was for you. Nope!