"DeLeo" is or was one of the interior fabric and coated fabric (vinyl) suppliers back then. If you went into a trim shop and looked in their trim books, they were probably DeLeo books. Kind of like "industry numbers" that are put on particular application brake shoes/pads. In another respect, it's something of a universal part number that people in the interior fabrics industry understand or reference off of.
There was a similar "book" made by another supplier, but I can't remember who it was.
On the DeLeo book, there usually was a lion's likeness that kind of reminded me of the one that Chrysler used during the "Golden Lion" era.