We were all correct, you, ckuan, and me. I back pedalled by re-installing my previous version El Capitan V10.11.5, and my Safari reversed to V9.1.1. That indicated this Safari version to be part of the OS installation.
I then upgraded again to OS X V10.11.6, which also included Safari V9.1.2, part of OS installation.
At this stage I had never seen a separate offer on the App Store for a Safari update, and a search did not come up with any result either.
I then installed the security upgrade 2018-001 for El Capitan (there are several security upgrades by that number for other systems). After that installation, the separate Safari upgrade for V11.0.3 showed up in the App Store. I installed it to bring my system up todate.
Thanks for all your input.