A little-known variety exist on 90-91 Bowman NHL Hat Tricks subset cards. Each of the 22 subject comes in two varieties: Single asterisk * before copyright on back or Double asterisk * * before copyright on back. Some versions are tougher than others depending on the player. Building a master set can be a real challenge!
Junk Wax Gems 
Thank you for posting this up. I can help with the following information:
1990-91 Bowman Hat Trick Tiffany Cards have the thicker gloss on the front, and out of the two sets I have opened, each copy of the card had the double **.
1990-91 Bowman Hat Trick cards have the “scratchy” gloss on them and the tend to curve the opposite way of the tiffany and lay more flat. I did find “*” and “**” variations among the cards I have with the “*” being more rare.
I started looking around more through my 1990-91 Hockey Cards and it looks like the 1990-91 Topps regular cards have sheet variants. I can not confirm if all “C” sheet cards have a “D” counterpart, but all the “D” sheet cards I have had a “C” counterpart.
The 1990-91 Topps Tiffany cards only have A, B, and C sheets, but I did not find any D sheets in the two complete sets I have.
I can provide scans if needed.
Thank you for making 1990-91 fun again.
Thanks for the info, Shawn! I just recently broke a few 1990-91 Topps Hockey boxes and I too noticed the C* and D* variations, especially on the team cards. Also, you’ll find that there are variations on the “hockey stick” design on the background of the card backs: sometimes they have the little “swooshes” under the stick and sometimes they don’t or only have one “swoosh.” Also, I am unsure if it was corrected, but check out Tomas Sandstrom’s card when you have a chance, especially the Stars player – very odd!
I may be missing something with the Sandstrom card. I have three regular and two tiffany versions and they all look the same. Maybe you can point me in the right direction. Also can you confirm if you have any different variations:
#78 Zarley Zalapski A*B* (both the Tiffany and the regular have the A*B*)
#80 Flyers TC has not print sheet identifier (Can not confirm what the Tiffany version has since I sold them)
Checking to see if you have any different versions from the cards listed above.
Nevermind. I see the blue triangle now. The Topps Tiffany version does not have that.