The special onion ring join has been studied before here at tatting @BellaOnline.com. There are many patterns using it to practice the technique. This pattern is the oldest one I have in the files at this time.
Recently, this mysterious doily was rediscovered on Intatters and caused a commotion. I was so pleased to know that even after more than a decade this doily is still being studied and worked by tatters. Patty Dowden of the Intatters discussion group on this doily, has prepared a new set of diagrams