Rich, I did check my plate septums against the film ones. The plate septums are approximately 2mm wider and taller, beside being deeper. The number markings do not coincide with those of the film septums either. If Graflex made a set of 16 film septums to fit the plate mag, they would have to be numbered as the plate septums are.
Chris

Just an update to revive this thread. Thanks to fellow member Barney, I now have a 4X5 bag mag with a mint- bag with liner. I haven't forgotten you, Barney! After much patient looking, I have found the mother of all bag mags. An 18 shot wonder with an exc+ bag, no liner, for my 3X4 pre Anny. That ought to be enough film for a week of shooting. After studying these things for a while, I think I've figured out why they started lining them. The liner helps protect the bag where the corners of the holder rub on it when changing. I suppose a little more protection against light leaks, too. Those holder corners could murder a bag if not careful.

Glad to hear that Glenn! Thanks for the kind comments.
Merry Christmas to you and all if I don't chat between now and then!