AR$100 in monedas might say "I appreciate what you do here." more than any chocolate, wine, dulce de leche...
Every week I make a special trip to the bank to get AR$20 in monedas for our lady and she is extremely thankful. The banks, in their infinite laziness, are only open 5 days a week and for only 5 hours a day (10am-3pm). Our lady works from 10am-3pm (and I think she works the same hours or longer at her other locations during the week) so she can't make it to the bank.
Monedas, monedas, monedas... unless you think of something nicer.
-N