I needed that clamp for a bumper Omega of my own. When I was unable to find one, I fabricated one. These movements are usually secured in the case by a steel pin on one edge of the case adaptor ring which fits into a milled slot in the interior case wall, and a “dog-leg” clamp (like the subject clamp) 180° away which is screwed to the movement pillar plate. The dog leg allows the case back to be screwed on. I think you have the right clamp.
It took me a long time to find the right clamps for my 351/2577 Sellers kept sending the larger 330 version.
Eventually I found an assortment of the correct clamps. I was about ready to fabricate my own using the fiber laser. This would not be a difficult part to make.
The downside I etched out some rusted screws and the pin also got etched out. I need to make a new pin. Something I keep procastinating on. So much easer to order a part and wait weeks or months. By which time one is already distracted by the next watch project.
O. Frie sells an assortment of 'Omega' case clamps. I suspect it is hard for the sellers to sort them. Even if they do like maximizing the profits selling one easy to loose part for inflated prices.