Paraphrased from elsewhere
" Sir Alexander Popham, an English seventeenth century
military figure, was painted in his equestrian portrait wearing a kasthane."
The Royal Armouries used to have a page dedicated to reviewing the portrait with glorious close-ups of his kastane. I believe there is a pdf showing some shots of the Littlecote Armoury, with a smaller detailed b&w view of the portrait. It has been posted here in the past.
It appears that the Dutch Indies trade were influential in the development of some form of hilts. From my brief look at kastane, it seems a subject one could spend a life in discovery.