The lettering looks more like Machine Doubling (MD). More experienced members will give their opinions. WWW.Doubleddie.com
Where specifically do you think you see doubling? www.doubleddie.com redirects to https://www2.briansvarietycoins.com/ for Jefferson Nickels (which there are no listings for 1979). Mentioning whether you think the doubling is on the obverse or reverse of the coin may be helpful for the future. DDO - Doubled Die Obverse DDR - Doubled Die Reverse I personally don't see any doubling.