XmMainWindowSep3(3) on Linux
The text 959cd33ba2a3, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A MainWindow function that returns the widget ID of the third Separator widget "XmMainWindowSep3" "MainWindow functions" "XmMainWindowSep3"