Art Young of the Ardiente Community Hiking Enthusiasts (ACHE) has submitted these photographs of the arrow associated with Los Angeles—Salt Lake Airway Beacon 31A (NGS PID GR1900). The arrow, which is referred to in the linked survey datasheet, is about 700 feet east of the former beacon site. The arrow has been painted orange since the images in Google’s satellite view were captured. It appears to be in excellent condition.
Art also noted that the Old Spanish Trail passes just a few hundred yards to the southwest of the arrow. The route of the Old Spanish Trail is mapped here: ArcGIS Old Spanish Trail Map.
Thanks for your contribution, Art!