The other candidate is from a lot longer ago. This was the Jaeger-LeCoultre caliber 145， which at 1.38mm is thinner than any version of the caliber 849， and which was made for a surprisingly long time – from about 1907 all the https://fmstaffingsource.com/employer/bonitaw2008/ way up to the 1960s. This is a pocket watch movement， okay， but it apparently was reliable， https://forum.aigato.vn/user/tawniej14 in the JLC movement catalog for over fifty years， and thinner than any current-production movement https://workaweb.com/candidate/farmanvtrinav/ of any kind， complicated or simple， hand-wound or automatic.