To date I've only found a few examples, and that was after 3 years of searching and close to a grand wasted on false materials. Like Joe, I have seen some examples on old tool boxes. But unfortunately the pieces that can be cut from them are way too small to be of any use. You have to have a briefcase size sheet for it to be workable.
Yep..what Joe wrote. If you guys are interested, I can photograph some sample I have and compare it to the modern stuff.
As close to impossible as impossible gets. But NOT impossible
After staring at Kydex for close to 4 years, I've become quite in tune with what's out there in way of vintage material. If you think you've found some, send me a picture and I'll let you know if you're wasting your money or not.