You kids and your "USB-C."
It’s an HD15 to 13w3 display adaptor cable I used to use to connect a KVM box to a big monitor.
(There were different kinds of 13w3; some were Sun, some SGI, and one or the other was also used by Apple; they had different pins and I forget the differences, but all had the three shielded coaxial wires and miniature sockets for video signals. The extra stability mattered back then.)