I have not been able to find it either.....However, if you are looking to grade them I can offer a bit of information....From my experience the boards from car radios are either mid-grade or #3 motherboard. From all of them that I have torn down they are not the highest grade of board but they will have some value. I even found one that had a low grade brown board in it, just my luck, I spend all that time tearing the darn thing apart and get nothing but crap.