Facebook launched a new API to give developers access to users' preferred currency and and the conversion rate to Credits.
As you may know, Facebook recently announced that it is phasing out Credits in favor of real money, and local currency (as well as a subscription payment model).
The API, Facebook says, lets game developers show prices in the user's preferred currency in their in-game stores.
"For example, a user visits your store to buy an item priced at $10 (100 Credits)," explains Facebook's Colin Creitz. "You can access the preferred currency — EUR for this user — and the current conversion rate from Credits to EUR via the API described below. Instead of displaying price in USD, you can now show the item price as €8.12 (100 credits * 0.0812 conversion rate). When you invoke the pay dialog, use the parameter "oscif=true", and the user will see €8.12 as the price of the item in the pay dialog as well."
Documentation for the API can be found here.