According to The Institute of Heraldry, this flash and oval was designated for the Long-Range Surveillance Detachment (LRSD), 1st Squadron, 18th Cavalry Regiment when that unit was part of the 40th Infantry Division of the Army National Guard. All LRSD Soldiers were Airborne qualified, and many also held Ranger or Pathfinder qualifications.
However, other reputable sources state that it is for Troop E, 1st Squadron, 18th Cavalry Regiment, which raises the likely possibility that the Squadron’s LRSD was redesignated as a standard Troop at some point in the early 2000s or perhaps even prior to that point. (A document on the Vietnam Helicopter Pilots Association Web site indicates the unit was designated as Troop E in 2004.)
In any event, 1st Squadron no longer has either a Troop E or LRSD in its force structure. The 1st Squadron, 18th Cavalry Regiment is a component unit of the California Army National Guard’s 79th Infantry Brigade Combat Team and is headquartered in Asuza, California.