Found these in my yard in the Pittsburgh, PA suburbs. First was found 10 days ago, second was found today. They are solid, not hollow. They are 4 1/8 inches long, 5/8 inches in diameter. One has some cardboard glued to one end. No other markings. I've lived here for 7 years, never seen anything like this before. The only new people who have been in my yard were two painters who stained my deck in this time frame.