Longines 420/428 – 846/847 (thin, 2,5 mm) – With ETA Peseux 7001 (2,5 mm) standard thinnest vintage movements

846-847

10.5”’, Dm= 23.3mm, Do= 23.7mm
H= 2.5mm
F= 1.0mm
T= 1.3mm
17 jewels
f = 21600 A/h
power reserve 40h

Balance staff U3307

Stem W3243

Hands
1.30 x 0.70mm

micrometer regulator, Kif-Ultraflex:

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&&2uswk&Longines_846

420-428

standard regulator, Kif-Flector:

In the 1970s, Longines resisted manufacturing quartz watch movements and instead developed ultra-thin mechanical movements. These thin movements bridged the gap until Longines joined the Societe Suisse de Microelectronique et d’Horlogerie (SMH) in 1983 — the conglomerate that would continue to evolve into the Swatch Group.
https://www.gearpatrol.com/watches/g37024576/longines-watches/