seedeeveeI believe it's actually British and it's way more expensive on Amazon but you can find them the same price or a little cheaper other places. I think it's because they are vintage that they are so expensive.
gmdietz"In 2003,[5] The Rayware Group purchased the design, patent and trademark of the original Kilner jar[dubious – discuss] and continues to produce them today in China.[6][7]"
Dubious or not, it seems inevitable that if these were made in the UK, Massdrop would be telling us so instead of hiding behind madeinchinanonymity.