I made a trade with a Numista member in Uruguay and he was a really honest and friendly swapper. I sent my coins regular air mail and they arrived in 17 days but my swap partner sent his by registered mail and they took 26 days to arrive. I generally only send by regular mail since I usually just trade common low value coins and I can't justify the silly money to send registered. The most important thing when sending coins (cash) through the post, whether registered or not, is to make sure the package is sturdy and the coins are secured between cardboard to make it harder to tell what is inside.
Just because you can't see it ... doesn't mean it isn't there - Anon.
Before sending check if the postal service is not on a strike in Uruguay. last notice I had was on August 20. Brazil's postal service stopped sending anyrhing to Uruguay due to this strike.
