Stamps from Brazil

I received some stamps from Brazil today which included the "Preserve the Polar Regions and Glaciers" issue. I was just as impressed with the cover they came in though. Normally I just clip the stamps and toss the envelope but this one I decided to keep. It's got a row of nice Brazilian stamps from the 90's across the top. Registered mail. Cancelled in Sao Paulo. Unfortunately my postal center wrote "D720" in felt tip marked across the top. That's what happened when the mail carrier comes by for a signature and you're not around... oh well.