It was most likely a Hunter One Trigger. Hunter Arms, HOT used a slide that took the place of the front trigger spot in the trigger plate. With the gun lying on top rib, it would be in the left slot. It had a small circle I believe made of copper, with an "L" stamped in it and rearward it had another circle with an "R" in it.
You could also order a single trigger in the forward position, middle, or rear. Most I have seen are in the rear position.
Some will have on the front of the trigger plate, Hunter One Trigger and others will have it along side the trigger.
