Leave the books at home. Be ready with a reference catalog whenever you see an interesting note. Every collector knows the moment. You're at a table at a regional show, a dealer slides a small-size $10 across the case, and something about it isn't quite what the flip says. The seal looks right. The series says 1934A. But is that the North Africa note, or the ordinary blue seal that someone has described generously? Your Friedberg is on a shelf three hundred miles away. This i