Just discovered there are actually two variations of both the third and fourth issues from Winnavegas Casino in Sloan, IA. Turns out there are cards with both a full WINN background pattern on the front as well as cards with a blank area for printing the player info at the bottom. All four cards have the same reverse. The guides never mentioned the front WINN background pattern and these variations were never documented.
Here's scans of the cards I'm talking about...