The recall was to replace the original thumb button with a key lock. Most of the caps stayed the same, but Honda swapped them as a kit at DOT's request. The original thumb button required that the user push down on the cap while pressing the button to unlock, then release the cap. The morons in the DOT thought this was too complex. Honda did this "2-hand" thing so a tank bag would not bounce the cap open, and from personal experience I can say it worked perfectly. The DOT swore in court that a rider's crotch could bounce it open (honest, you can read that transcript yourself!), and made Honda retrofit every CB750 out there. (If your crotch DID open this, you would never have had a chance of having kids...)
I would have kept the thumb button, but the bike insurance I had at the time would not renew unless I sent in the "certification of safety retrofit" paper that Honda gave out with the early kits, indicating my bike was "fixed".. (This was American Family Insurance in Illinois, circa 1973.) Now, it needs a key (or screwdriver) to open it.