Sheet metal or tin carrying cases were popular with the British from the early 1800's. I have seen military examples in museums here in Canada, often with the officers name painted on the outside. Occasionally, in antique stores you see the leather cases for the beaver top hats. I think the "cone" shape is unique to the hauben but again I could be wrong in throwing that idea out for discussion. All of the pickelhaube cases I have seen have been cardboard with leather straps and handles. Some have round metal studs on the bottom for protection. They are often lined with cheap cotton cloth padding.