The length of the bar sure seems to put it in the panel gauge category. I'm looking at it and wondering why the fence isn't square to the bar... It looks to me like the wedge got put on the wrong side of the bar at some point. Those aren't, I don't think, two wedges. Two wedges doesn't make much sense. More likely, the one with the keepers is just to keep the edge of the rather thin bar from getting crushed.
Try pulling out the wedge, then the bar, and swapping sides for the wedge. Betcha it will square up.
I do think it is user made since all the panel gauges I've seen have thick bars, I don't think it's Japanese. While I have a thin bar marking/slitting gauge that is Japanese, the ovalo details on the ends of the fence aren't the sort of things I expect of Asian tools.