Longines - Mens Ultra Chron Cal 431

 Longines

Longines Ultra Chron Mens (ref 210) Purchased 14/03/13
Serviced: watchguy 08/04/13 (ref 163)
The movement of this watch is a cal 431 Longines 17 Jewels adj 3 positions dated 01/06/1970
Data
11.5''', Dm= 25.6mm, Do= 26mm
H= 4.9mm (5.0mm with ball bearing)
F= 1.8mm
T= 2.0mm
17 jewels
f = 36000 A/h
power reserve 40h 

    Features

automatic

sweep second

date: set by changing 22:30-24h

Gold plated case.

A link to the service of this watch is here. "Watch Guy" Repair

I contacted longines directly and was very pleasantly surprised to receive a reply but even more surprised to be told the actual date of manufacture which was June 1970 originally being invoiced to Longines-Wittnauer in America. This caliber of movement was first produced in 1967.
It's a lovely watch in both looks and movement quality. Longines in general for me is a lovely brand of wristwatch and this particular hi beat movement is quite important as it was a last ditch effort to ward of the inevitable march of the very accurate quartz movement. It failed just like all mechanical watches as the price alone was unbeatable.
The seconds sweep on this is as seamless as they come with hardly any ticking noted at all.
Special lubrication is needed due to the high beat nature.

Before Service

After Service

That shows the difference very nicely indeed. Double amplitude and running very accurately with a slight adjustment of 3s a day dial up

The Mainspring cannot be changed alone due to the strength of the spring so you change the whole barrel and mainspring.