I'm working with a batch of tapes that includes several IBM Series 500 7 track reels. If you look at the back of the reel, there's no customary thumb recess for removing the write ring. Rather, the reels have a small red plastic peg that extends through to the front of the reel. Is this for ejecting the write ring (I haven't tried)? In any case it's a bit annoying because it grazes the edge of the ring sensing finger, making a little "click" every time the reel makes a complete revolution. --Chuck