Four or five different sources on the internet credit RJ Grunts and TGIFriday's.
It's possible, sure. But TGI Friday's didn't come up with skins until their Dallas location did it in 1975, and I found a Rio Cafe menu from 1969 that had em. What's more interesting to me, is to HOPE that they weren't just invented around the same time by multiple people (the most likely case), but to think of how information traveled at that time, and how people could have found out and copied a recipe from another restaurant. The Rio Cafe was NOT in a good part of town. 1st Ave in Seattle was nasty at that time... the most porno theaters anywhere in the world, apparently. And some guy from Dallas visits Seattle... and happens to eat at the Rio? Or someone who had eaten at the Rio was a friend of a guy in Dallas and talked about their 'skins' they'd had at the Rio? I'm nostalgic for when information was scarce.