My first response was that it might be some kind of farm implement, like a horse drawn tiller of some kind. But I don't see any images on google that are anything like this.

I didn't see any fittings for a saddle. But googling "history penny farthing blacksmith" images found this history of bicycles in Japan. The whole bike, including the wheel, looks like it was handmade from iron and steel. (or is the wheel made of wood spokes and rim?) I'm guessing it weighs 100 pounds?

The saddle just clamps on. And the step by the rear wheel is clamped on, too.