Not an avid collector, so take it anything I say with a grain of salt.
1) It is certified, so it's got that going for it.
2) The felt tip pen became popular in the 1960's and Risberg died in 1975, so that was plenty of time for him to have signed. These two factors are very much in the autograph's favor.
If doesn't nail the exemplars I found, however. You have to decide how much that bothers you.
https://images.psacard.com/s3/cu-psa...424.jpg?h=1000