Funk, I owned a style based on that design. That model also resembles a version Bruce Lee owned and used that was auctioned off at one of his estate sales I believe.
By far, my favorite gripper device I've ever used is a model made by Hammer Strength:
nice never saw that one before, i had one similar to the one i pic'd sold by lurie's it was a piece of junk it was not welded right or something would bind up and be impossible to use. i have heavy grips now, they come in strengths of 100, 150, 200, 250, 300, 350 lbs. richard sorin was said to be the first guy to close the captains of crush # 3's which are rated at 280 lbs so i was curious to what guys on here could do. my grip is pretty pathetic anymore can barely squeeze the 150's anymore. funk jr aka john can close the 250's even now in his diminished state down from 230 lbs to 150. he used to do some grip stuff like picking up 50 lb york globes with one hand by the bell etc.