I think the prototypes had an extra STEPS target/insert, but I don't know about sample games, you can see information about one here: http://www.hsapinball.com/HSA_PINBALL/hsa34.html
If you're having trouble with mylar gunk removal I'd recommend trying citrus oil (IN THE MOST HIDDEN SPOT POSSIBLE, AT YOUR OWN RISK, ETC.) because I've had great luck with that the two times I removed mylar. Something like this: http://www.amazon.com/Air-Therapy-Orange-Original-Ounces/dp/B00DX5IYC0/ref=sr_1_1