Franklin Leather

I asked this question recently in the Easton group but didn't get a response. Does anyone know the kind of leather Franklin used in its various series? I know that Easton uses pigskin in its regular issues and Italian cowhide in most of its DLEs. I also know that Folio uses goatskin. But I've been unable to learn what Franklin used. Their books are noticeably heavier than similarly sized Eastons and Folios, but I can't tell if that is due to the leather or the paper.

I too am interested in this.

I was close to a 25 year subscriber to one or more sets and use to read every word of their brochures. They never to my knowledge mentioned the type of leather they used on their books.