Longines "Anti Magnétique"

Following from @J_pilot's recent post about his 13.33Z (https://omegaforums.net/threads/my-13-33z-18k-chrono.101697/#post-2265101), I am starting a thread to collect information on Longines watches with dials that denote "Anti Magnétique" or some variation thereof. It would be neat to see early examples with these markings. It would also be neat to compare their balance wheels, levers, and hairsprings with examples that lack these markings.

The first comparison below is of two caliber 13.33Z examples. The first example (4'86x'xxx) has a dial that is marked "Anti Magnétique", and a monometallic balance wheel. The second example (4'981'741) has a dial with no such marking, and a split bimetallic balance wheel.

The second comparison below is of two caliber 19.73 examples. The first example (serial not visible) has a dial that is marked "Non Magnetic", and a monometallic balance wheel. The second example (2'236'950) has a dial with no such marking, and a split bimetallic balance wheel.

Source: https://omegaforums.net/threads/my-13-33z-18k-chrono.101697/



Source: https://www.wristicons.com/longines-1333z-chronograph-1930.html



Source: https://mystagogie.jimdofree.com/page-d-accueil/chronographes-de-poche/longines-19-73n/


Source: https://www.ebay.co.uk/itm/125239901302?hash=item1d28e13c76:g:Q4MAAOSws5llV3mr&amdata=enc:AQAIAAAAwDHuz1wmI2fhGbeB07YSL2Yf8Ea6e2uH0Q4kBfu6Kje5kLVKLmmZAOUAAN09R3/M1R0vHN++R9wqr/WZK/yty2lpwpnytPb2cdxqOzQIUTg61CTFG9MNcIyf8+t/zgMqfOclhXH/HG9aU1jC5e67z0JgwMIk4zYr9g8SJIb8g+3YwgzBiIcPAXjh15mMbV78oJ1dFqztn3lhcYqoHx7aBnklJVDHPTk6H7SviB7qVbbtKhK3ZzWXwHTEprNTlLwHAA==|tkp:Bk9SR_SyqaCBYw

Here is a caliber 19.73N example. The dial is marked "Anti Magnétique", and the balance wheel is monometallic. The serial number is 4'569'091 and it was invoiced to Italy in 1928. Notably, the color of the balance wheel in this example is similar to that of bronze, whereas the monometallic balance wheel of the 19.73 example above looks more steel-toned. Below is a comparison of the two movements. Along with the different balance wheels, the calibers differ in a number of other ways (e.g., column wheel design, design of chronograph cocks, pin-set versus stem-set).

Source: https://www.phillips.com/detail/longines/HK080220/938