http://www.nevada-history.org/paper_money.htmlhere's a nice source.
Just to clarify this point, I reread it and it wasn't very clear:
The bills are worth FAR more than their face value and the bigger issue is trying to pass them off in collector's circles.
What I was saying, is it
is Illegal to copy bills that the state is obligated to endorse. The rules are more lenient for these old large size bills (color copies are permitted, for example) because they aren't in circulation anymore.
Any federal bill from 1862 onward is still legal tender -- you can take it to a bank and the government has to honor it for the value printed on its face.
Since the old bills have far more value in private collector sales, no one in their right mind would ever try to copy an old bill and try to use it to rip off the government -- so it is not something they are concerned with and interested in spending resources to enforce.
The people who would be concerned would be private collectors.
As a point of interest, I gave one of my bills to my supervisor at work. He took it with him to the bank (a large chain, no less) when he was depositing some work money and jokingly tried to cash it (don't do that!)
They all got a big kick out of it, even the manager -- not even a warning about counterfeiting. Most people probably don't even know the details.
Still good to know the facts.
So in all honesty, i can't see a situation where people printing these bills for props would even raise an eybrow -- just don't try to circulate the damn things.
State currency from the civil war era, etc, is totally legal to copy.
Gold and silver certificates may be too, i am not sure about that.