Jennifer makes a very good point. There is no way that you can ever be
completely sure that you're not accepting tainted money. Indeed, I'd be willing
to bet that there are bloody few major corporations whose hands could be found
to be absolutely squeeky clean over the years - and that undoubtedly applies to
a lot of individuals, too! As Jennifer says, hindsight is a wonderful thing. It
sounds like her institution's sanitization job was very effective, even without
the use of sandblasting.

Harry Needham