I don't know a lot about the 1886's, but in the old days Winchester used to sell lower tangs for 1885 single shots without serial numbers. It's not super rare to find an 1885 like that so maybe the same for 1886's? This was often done if someone wanted to reconfigure to a pistol grip or set trigger on the single shots.
When you go to shoot it, be aware that the 45-90 lever guns used a slow twist rate so were meant for quite light bullets.
Chris.