I gave a bonus tip to a tour guide in one of these countries.

I'd brought USD notes from Europe to spend and as an emergency fund. They were all brand new (sequential numbers) $50 notes, just what my bank gave me.

At the end of the trip, I swapped about $300 of old notes the tour staff had for $300 of new notes. This included a very slightly damaged $100 note which the tour guide said had been a tip, which he was unable to use because of the damage.