JLC 849 is 1.85mm
VC 1003 is 1.64mm
They are twin brothers.
The 849 is a redesigned version of bridges in a typical « Vallée de Joux» style of a much older calibre (calibre 839 from the seventies) to show through a sapphire case back. I just love it, although I have a 33093’s 1003 but no 849 yet. The original 34mm ultra thin is a goal for the future.