This Ring Sight came into the possession of the Comox Air Force Museum in British Columbia. Was wondering if anyone could identify what type of weapon it was mounted on? It appears to be oval shaped and slightly angular.

Could this possibly be the Ring Sight attached at the rear of a 1st or 2nd World War version of an air gunners British 303 Lewis or Vickers Machine Gun? The base of the Ring Sight has a single cam and bearing pins on either side allowing it to be flipped up or down. The Ring Sight is quite tall which leads me to think it was possibly mounted on a Lewis or Vickers as the pan magazine was obstructive for gunner, the Ring and Bead sight's height allowing for unobstructed aiming.
Ring Sight ... weapon type?