I love this idea ... you could have tons of fun with it. Pull your car into a public parking lot and pretend to be having engine trouble. With the "mystery piston" hidden in your coat, pop the hood, pretend to wrench around a bit, cursing all the while. Then subtly pull the piston from your coat as though you pulled it from the engine, toss it across the parking lot, brush off your hands as if in victory and then get back in the car, start it up and drive off ...
For 99 cents it would also make a fine doorstop or, if you're into that Ruby Tuesdays style of decor, a nice accent piece for your dining room wall ...

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)