First of all, very nice coin! And AU58 I think is dead-on. I wouldn't mind owning this one just for what it is. Regarding: I am going to assume you meant to say "more than 15 degrees". From what I can see, the rotation on this coin would not even pique my interest as a rotated die, & I believe most collectors pursuing die rotations would not find this significant enough either. Regarding the "reverse clash", I'm afraid my eyes fail me, but it certainly is one proud buffalo, congrats on owning it!
Wait a minute. Is the reverse picture upside-down? Is the top of the slab at the bottom in that picture? If so, sure, that's hardly much of a rotation at all. I thought in both the obverse and reverse pictures the slab was oriented right-side-up, that's why I called it a 180.
It's closer to coin alignment than medal alignment. I only noticed that this had a rotation after purchasing the coin raw. Thinking that it fell within NGC's minimum die rotation requirement, I submitted the coin as a Mint Error with Rotated Dies.
I used TurboCAD. To be honest I don't really know if the rotation is 14.02 degrees. Look at the following two groups of images. Tell me which image from each group represents the coin design @ 12 o'clock. I'll tell you the rotation spread is four degrees in each group.
For the obverse, the first one in the first row, and the first one in the second row look straight. For the reverse, the last one in the first row, and the middle one in the second row look straight.
When I did the original overlays - I used the middle image in the 2nd row (2-2) for both the obverse and reverse. This is the orientation of the sources images from which the CAD renderings were created. The images you selected for the obverse (1-1, 2-1) have a .5 degree spread in rotation. With the largest rotation difference of 2 degrees between yours and mine. For the reverse - one of the images you selected is the same image I originally used (2-2). The other image (1-3) has a 1 degree rotation difference. There is a reverse image with only a .5 degree rotation difference from image (2-2) rotated in the same direction as image (1-3). Point being due to the fact coin designs are circular in nature as opposed to linear determining the 12:00 o'clock position begins with a guess. Anyway putting everything back together - using the images you selected that produces the greatest rotation (1-1 obverse, 1-3 reverse) - the results were as follows.
Thanks for that! I'll send this back to NGC to re-evaluate it for the rotated dies. I should really get AutoCAD and learn how to use it... takes a lot of learning and studying from what I can tell though.