Sorry I didn't get to pitch in on this earlier but I just joined the site. It is as you says bandsman's lance cap made by a firm based in London called 'Cashket' as I recall. I understand they were rejected some time ago 1990s because if they were dropped they tended to smash. After that the bandsmen's pieces were put together by Louis Chalmers who make the plumes for the household cavalry. He worked with a chap called Paul Scarrot-Jones and they produced czapskas built as the originals with leather bases and stiffened cloth pavilions that stand up to use far better.
