Got to be the Washington "Big Heads" (not the old 100's style with the small George Washington portrait). Get 2006 or later notes. 2009 even better. No CB serial numbers. Notes should not be torn, marked, overly folded or creased, etc. A simple single fold or crease is usually OK. A tall order, but all over SE Asia, these more perfect notes are demanded. The only reliable way to get them is old fashioned manual effort. Inside a bank branch. Preferably when it's not too busy since the tellers may have to take a while to round up decent notes from different windows or from the back.