Errors are rare, and they are out there. But you seem to be trying to find things that are impossible.
Best thing for you to do is research it for known rpm's and compare it with photos. A USB microscope will make deciphering rpm's much easier. It is impossible for us to see in this photo.
If you check your Redbook you'll see that prior to 1964, the last Nickel with an S mm was 1955, nine years before (the S mm was resumed in 1968). You can find a lot of info in the Redbook that will help answer the some basic questions Wait, don't have a Redbook?? Buy one! Best $10-15 you'll spend. You seem to post a lot here and this book will definitely help you learn about coins. Not much on errors but you would be able to see how unlikely a 1964 s/d would be
