The Market Converter allows a player to convert one of her worlds into a market, which means other players may trade on that world. Market worlds also have a special icon and their own category in the world tab.
How to Obtain
Can be purchased in crowns store or traded.
How to Use
Go to the world you want to change into a market. Move the Market Converter to your hotbar and select it, then click anywhere in your screen and select the appropriate option in the dialog box.
Note that since trading is automatically allowed on private worlds by default, the Market Converter is only useful on worlds that you purchased and then made public.
Beware when trading for this item, as it looks just like the Scale. Unscrupulous traders will offer to sell you a Market Converter and then switch in a Scale instead, so look carefully before accepting a trade for this item.