I ran across this during a recent move. It's an EPROM we used during the final test phase of Secret of Evermore in late 1995. This would be a near-final beta of the game. No, it doesn't contain any secret, hidden unreleased stuff. We were too busy furiously trimming tiles from levels in our attempt to fit on the cartridge to leave in anything remotely like that.
I'm tempted to boot it up for old time's sake, but I have my doubts about that battery. I should also review which direction the board faces when you plug it in: EPROMS can be plugged into a console from either direction (chips towards or away from the player). Finished retail cartridges prevented that but during production we had to be careful. Facing the wrong direction would wipe the whole works.