Quote Originally Posted by Cosmic View Post
The big secret about the five screw carts is they sometimes contain Famicom chips with a converter. Which means you can open the cart, remove the converter and use it to play Japanese titles on your NES.
Not to mention that there are some that are pretty rare rare. For instance the DKJr Math previously mentioned. I saw one in not too great shape sell for $125 on nintendoage forums. The Famicom convertors were in some of the really old NES carts too. Mainly in copies of Gyromite though.