Type I features a high center Olympic ring.
It also features a normal, strait snake tongue.
Type II features a low center ring and a normal snake tongue.
http://www.coinpage.com/large.php?tImageId=1537
Type III features a low center ring and a long curved snake tongue.
http://www.coinpage.com/large.php?tImageId=1538
I think I have that info right.
If not, maybe someone can correct it.
It looks like the Type II and Type III are worth more than the Type I, in uncirculated grades, but I would hardly call any of them "valuable".