There are very few 1969 S dd in circulation, but there are some. There are probably zero 1955 dd in circulation. They are all in collections. (dealers, etc.) You can buy a 1955 dd but looking for one in circulation is not really going to produce anything. If You Tube is telling you that you can find a 1955 dd in circulation, then that's just another blatant lie. You could find a Chinese fake in circulation, as there are more of those than real ones.
Thank you Michael K, I was actually being sarcastic when I mentioned the doubled dies. Indeed the example of 1955 might not be so successful but I was just trying to make a point that I find coins that require questions, because I am still learning, while a doubled die is easily recognizable. I quit watching YouTube videos a long time ago, so that won't be a problem of me getting misled. Thank you for your time. I really appreciate your intention to help me out.