Hello
Can't help with exact identification but I also can't resist the need to muse on how it may have been used. Once the gate is closed on the rope/wire and a load is put on it, it looks like a pull back on the solid handle (lever) would cam the gate more or less open and allow the line to be released while under load. The bottom looks like a fulcrum for the handle lever, to make it easier to pull all the way back. This fulcrum also suggests that this tool was employed along a solid surface, like a wall or boom, etc. A test of this would be interesting.
Dave