I have tons of grippers. CoC are very good. (Randy (Dr. Strossen) is a friend of mine that I see at the AOBS dinner on occasion). And some of the CoC knock-offs are good.
I bought an original Ironman Gripper from the 70's years back for 20.00 at the AOBS dinner of of a friend.
I mentioned it on Dr. Strossen's forum (Ironmind), people were going crazy asking me to sell it to them.
I tried ebay, and got 350.00 for it
Its sort of a cult (visit the "Grip Board") but a fun hobby never t he less...
The Bruce Lee gripper is actually my fave.