Items are given an iron value when sold, this is equivalent to 1 iron per 10ql plus 1 iron, minimum being 1 iron for a 0-9ql item.
You can earn up to 5 copper per hour maximum by selling items in this way. When you hit the maximum, you'll get the message: "You have sold your quota for now."<br />Once you get this message, you will be able to sell again one hour after you sold your first item. (Needs confirmation)
Certain items cannot be sold this way, including liquids, scraps, dirt, clay, needles, rock shards, nails.