Okay, guys...verdict is in...I do not believe that this is an S. limbata ooth. Possibly S. carolina or S. californica, but definitely not S. limbata.
Below you can see the differences between the one that Alex sent to me and the Limbatas that my girls laid last year. (One large "first" ooth and a smaller "subsequent" ooth.)
The ooth that was sent me is not the right color or shape. It is not nearly round enough to be a Limbata. The fact that the "zipper" is already open worries me.
Alex, you said that you had been keeping it "cool" before shipping it, and it IS normal for those "fins" to open up as they are incubating & getting misted, but...it seems a bit early for them to be THAT open...it usually looks like this right before hatching, not a month or so earlier. And I looked at it under a 10x loupe with a flashlight & saw actual openings (into the ooth) in the fins (indicating nymphs have already emerged.) I will continue to incubate as if it is fertile & such, but as of right now, it doesn't look very promising. :no:
If nymphs do emerge, I will keep you guys updated.