Could they be pre-war Pacific double sets? I have them on a Krag varmint rifle, operation is by pushing the front trigger forward to set the rear trigger.

Kind of hard to see but there they are. (Pacific made a lot more stuff than just sights and loading tools. The grip cap and butt plate on this rifle, both made of aluminum, are from Pacific also.) Rifle is a .22 Maximum Lovell, built by Hervey Lovell, borrowed rifle rest and all.

[Linked Image from i.imgur.com]