Late reply here, but I was referring to the one-sided aspect. Just seems unlikely to me that someone would realistically intend for a one-sided copy of currency to be believed as real. Just seems like the threshold for printing both sides is so low that anyone who only printed one side must not really be intending for it to be taken as real, at least not for very long.
"Not for very long" - that's exactly the point of the currency-exchange scam:
- mark gets an offer of a great exchange rate from the con-man
- mark hands over real money
- gets a stack of something - the first few bills on the top and bottom are actual local currency, but most of it are one-sided counterfeits.
- con-man counts the money in a way that doesn't give this away - this obviously requires sleight of hand and insufficient lighting
- con-man disappears in crowd
- mark eventually realizes that most of the stack is worthless
The whole con takes a minute or two at most: that's not very long at all.
The critical section "mark no longer has original currency but hasn't yet realized he has been swindled" is as short as a few seconds; this has even been done with plain paper in some particularly audacious cases.
