It's definitely a developers prototype cart. I seen Glover and Miniracers carts similar to that one. Does it play in English or something else? Carts like that can go anywhere from $125-$450 dollars depending on the version and if the game was unreleased or not.
It plays in English.
I've got a dev cart with Superman on it. They are rare, but not super rare. Great find in a box at someone's house though !