Here you go Barry…..some notes that I made some years ago when the topic was mentioned and it inspired me to ‘investigate’ in case I needed to change mine at some point – and I found the piece of paper!
I also took photos at the time of the actual struts giving all the info….but I can’t find those, but the info is clearly on the struts.
I seemed to think that Billington group (as per Tom) supply or make them? and if I remember SGS may have been mentioned or came up in my search, or perhaps they manufactured them?. See a photo shot of my notes below