Today I found this 1925ish Longines pocket watch with what it appears to be a high caliber movement. 17.89 cal, 19 jewels, 5 positions. The case is 14k solid white gold and it runs. The above is about all I know. I see some references to the 17.89M in google but mostly 17 jewels and many without the snail regulator. I would love to know more if anyone has the expertise.