Unknown (for me) antishock system used by Longines in cca 1952

As noted above, I don’t think that actually is anti shock at all.

I have always thought that this was an anti-shock device, as well. It appears on a number of Longines calibers from the early 1950s, as well as all 30CH movements (as far as I know). Like most anti-shock devices, the cap jewel on the balance cock is held in place by a thin piece of metal. This thin piece of metal is not fixed to the cock, but held in place via tension. This is in contrast to designs without shock protection, in which the cap jewel is attached to a ring of metal that is screwed to the cock.

Caliber 12.68Z. Source: eBay


Caliber 23Z. Source: https://watchcharts.com/listing/450...alatrava-mens-military-sei-tacche-watch-steel

Caliber 22AS. Source: https://www.ebay.com/itm/3261871127...J3fOGP4hRqGUkm2r5AkYiLLASz|tkp:Bk9SR4639LWkZA

Caliber 30CH. Source: https://www.carsandwatches.com/watches/longines-30ch-pink-gold-special-case

I checked Patrick Linder's book, and "Shock-Resist" is mentioned for the 30CH. I also checked a caliber 530/538 repair manual from Peter's Vintage Longines Watches and found this:

Source (page 3): https://drive.google.com/file/d/1IX3_4tg_9lg91bZdiqrZfpGrFqd7WKso/view

Source (page 4): https://drive.google.com/file/d/1IX3_4tg_9lg91bZdiqrZfpGrFqd7WKso/view