How can you tell a dud from a pound?

eric idle said it in a sketch from the series monty python when portraying a scottish terrorist.

put it in a glass of water if it floats its a dud if it sinks it is a good egg

It should be fairly easy since the standard alloy 1 pound coin is yellow-ish and the silver one is, well, silver. The silver one is also a proof so it should have very reflective mirror like surfaces.

You should just walk up to her and just straight up tell her that you like her because it really doesnt matter about how much you weigh or how good you look its your personality that counts. so just...

30 pound is in the same size roll, but covers half as much as 15# and is twice as thick.