It's definitely not real IMO.
My buddy and his wife worked for Jerry from maybe 88 until he passed away. He would always stash stuff away when Jerry would have him clean up. At some point Jer had gotten a new briefcase and had my friend go in his closet and get rid of all of his old briefcases. He just threw them in storage. Recently we went through the briefcases and one of the inside sleeves of one was not emptied out. There was a treasure of collectibles in there. One of them was this signature. I’m sure it legit.
Here’s an item that was in there that was pretty spectacular. Sweet doodle
The RocknSports one in the OP is 100% a forgery and not a good one. The one from the briefcase looks good.