Vintage Rolex as an example a 5513. Serial Numbers are stamped on the case not on the movement. So if the movement is totally wasted -say a 1520 movement as an example- and you find a new one or a good used one- and install/replace the wasted one using the same case, no issues since no SN on the movement. It is a totally legit 5513- no need for an extract, no need to know how this 5513 really was sold as a 5513. And yet some Rolex timepieces use the same movement. Not true with Omega SM 300 with caliber 562 or 565 correct? Different Omega models use same movements hence the need for an extract using the movement's SN to prove authenticity as to whether it is a legit SM 300 or just a right movement in a wrong case. If I am correct, which one is better? Thanks.