AM 640

AM 640 | - The Movement Archive

AM 640


In the 1920s and 1930s, AM (Adolf Michel SA) was one of the largest swiss ebauche manufacturies, but after the Ebauches AG merge, they kind of vanished and today, only very few people still know about them.

The rectangular caliber AM 640, a form movement with a width of 6 3/4 from the 1920s is the base caliber of the caliber family of the same name.

AM 640: version with 17 jewels

version with 17 jewels

It is unusual for the 1920s and 1930s, that this movement was available with 17 jewels, too. Here, the minute wheel was beared in two ruby bearings.

AM 640: base plate

base plate

As expected, this pallet lever movement was well made, and of course all important bearings contained rubies, so that it used in total 15 or 17 jewels.

AM 640: base plate (17 jewels)

base plate (17 jewels)

It is nice to see, how, because of the age of this movement, all ruby bearings were still edged and not just plugged into the plates.

AM 640: gear train bridge (17 jewels)

gear train bridge (17 jewels)

Although the available space was not completely used, the rectangular shaped allowed the usage of large wheels. Their arrangement follows the usual scheme mainspring barrel - center minute wheel - third wheel - seconds wheel - escape wheel.

AM 640: gear train

gear train

The crown wheel has got a left-hand thread (not marked).

AM 640: side view of the gear train

side view of the gear train

The two leg screw balance (bimetal or monometallic) is of course not yet shock protected. It beats with 18000 A/h and can be regulated with a long regulator arm.

As escapement, a swiss pallet lever escapement is used.

AM 640: AM 640: Dial side

AM 640: Dial side

Of course, the AM 640 uses a yoke keyless works (whose setting lever spring is unfortunately broken on the specimen shown here).

AM 640: dial side, version with 17 jewels

dial side, version with 17 jewels

The 17j version has got the AM hallmark on the dial side, which makes the identification of the movement a little bit easier.

Technical data

Caliber base:AM 640
Size:6 3/4''' (measured: 15,0 x 24,5mm)
Number of jewels:15/17
Escapement:Pallet lever
Balance types: monometallic screw balance (two legs)
bimetallic screw balance (two legs)
Shock protection(s): none
Balance bearing / direction hairspring:Counterclockwise
Moveable stud:no
Adjust mechanism:Long regulator arm
  • lever
  • escape wheel, seconds wheel, third wheel, center minute wheel
  • mainspring barrel
Construction type:solid construction
Winding mechanism:yoke winding system
Attachment of setting lever:screwed
Setting lever spring:2 hole(s)
References: Ebauches: 1928
Feilner: 13 488
Flume: 1944 80 315201
Jacob: 1942 32 15048
Inventory number:23010

Usage gallery

AM 640: anonymous gents watch (15 jewels, case missing)

anonymous gents watch (15 jewels, case missing)

AM 640: anonymous gents watch (17 jewels, case missing)

anonymous gents watch (17 jewels, case missing)

This movement in the 15j version is a kind donation from Rolf to the movement archive. Thank you very much for your great support!

Caliber Family
AM 640

Other movements from AM