title_body: What is the clear plastic sticker on New England Coffee bags for?
upvoted_answer: Good observation in both meanings. Yes, the transparent thing is for freshness. It is a one-way valve for the coffee to release redundant CO2 gas out of the package.
  
  A more common form can be seen here.
  
  If you want to learn about how CO2 is emitted, you can search for degassing.