That wrap showed up on German drums in the late 60's. I'm not sure when Sonor started using it but Tromsa made quite a few drums from 1968 on for a while. It isn't Nitro Cellulose----I think it is Acetate and it is very brittle and prone to cracking, especially around the lugs, when they loosen a bit and start creeping. Sometimes the buckling can be flattened out by using gentle progressive clamping over time and then ,making sure the lugs stay tight.
I've had some success bringing separated cracks back together but they are tricky. You need a combination of friction ,pressure and heat.
This is a very beautifull wrap in the not so common Indigo blue, with varied intensities of blues weaving in and out----kind of like , the wake of a boat ,cutting through deep blue water at sundown. . I would preserve it but there is a dark blue onyx out there and although not the same , it would do the drums justice but cost a lot.
This one was Blau Schiefer (blue schale) for Tromsa. Tacton also used it .