Here is the information quoted from this site's main page.
"While the boards are mainly intended for information exchange, there are instances when an individual may wish to post something for sale to other collectors on the individual forums. If you wish to post an item for sale, you must be at least listed an “RKI Member.” You may also post items for sale if you are listed as a “Long Time RKI Member,” “Respected Member,” “Technical Expert,” “Industry Expert,” or if you are a Board Moderator. Only post items you actually have in your possession – do not post future expected items that have not been physically received yet. If you purchase something listed on the boards, you assume all risks, so understand the seller's terms of sale, return policies, conditions, type of payments and timeframe of delivery prior to your transaction. It is BEST if you have such details in writing, via letter, signed fax or e-mail. Again, All NFA Rules apply, and these boards are NOT primarily market boards."