I could help you if I knew what you mean with 'Scalloped' bottom ?
The Pz IV had several different Schürzen not only the Ausf. J but the Ausf. H as well .
Do you have a picture of the one you are writing about ?
P.S. it's Schürzen without a T ( I'm not trying to be a smart ass, I just like it to you US guys writing German technical terms, I'm from Germany.)