XmGetXmScreen(3) on Linux
The text 09db08b4bb26, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A Screen function that returns the XmScreen object ID for a specified screen "XmGetXmScreen"