There are not really two actual seals of Johann Sebastian Bach. But just one.
However, for a long time Bach Science thought the seal with the crown, which had exactly five pegs is the authentic one. Later the Bach science researched, that Bach back then created his seal with a crown and seven pegs.
Today both seals are spooking throughout the internet. On the internet one of both seals surely will never completely disappear. In actual publications authors probably will exclusively use the correct and "new" Bach seal.