I own a later example of the 1b, with the serial number 24797. I was suprised to see that the owner made an exposure and distance scale in the flap of the case. Just like the one in the Wiki catalogue here. Are there more Fed cases with a table like this?
I've seen a few of these. I suspect these case inserts were either sold or self-made from some originals. I've seen many cases with "additional features", of all makes, models and ages. People attach pens, pencils, brushes, etc. They cover cases with decals, modify the nose part to accept larger lenses.
These modified cases can probably be collectibles on their own:-)
I have too such a scale in one of my leather bags, but printed and not hand written, like in the wiki. It was for one of my 1b too, but I don't remember which one. Another interesting thing: some of these bags don't have a hole in the bottom to put a screw (bags for 1a and perhaps very early 1b.