Posted By:
Craig DHi,
Here's what I've found. Given a group of 100 various T3s, 55 will be from the 1st series, 45 will be from the 2nd series. Given a group of 100 2nd series cards, 60 will be checklist backs, 40 will be Turkey Red backs.
That being said, most people pay little attention to the back variations on T3s, so demand (or lack thereof) doesn't normally create a premium for the Turkey Red 'ad back'. On average, however, they are rarer.
Hope that helps.