FAL Israel, grenade launcher adapter (?)

This is supposedly an adapter for the ENERGA rifle grenade.  While earlier versions used a grenade launcher sight attachment, this model is supposedly for a later version where the plastic sight clips onto the grenade body or fin.   Fits Israeli and FN Type A lugged barrels only.  Will not fit G1 lugged barrel.  Note absence if traditional grenade launcher sight in gallery image (Grenade-mounted sight image  is a German unit by SADefense Journal)