A rock I’d believe, a coin? I don’t think anyones throwing a coin the length of a football field.
Well, a coin edgewise is more aerodynamic than the average rock - people throw playing cards over 100 feet - I've actually seen that done.
What coin would Washington have been throwing? I would guess probably a silver half-crown, which would weigh about two ounces - or about the weight of a golf ball.
Who knows?
But small objects can definitely be thrown 250 feet by a strong teen - especially if the wind is at his back.
After this conversation I have half a notion to bring some dayglo golfballs down to the high school track I normally run on and see how far across the football field I can launch one.