I don't think it can be a direct replacement for the original blue hammer.
The HAMMER name is now owned by a different company than the original, so this would be considered a "new" ball from them (as they were not the ones who originally made this), and I've heard that the specs of the coverstock on the old blue hammers would not be approved today, so no "new" ball with those specs could be made unless it was by the original company.
It may be good, and it may be close (if its urethane), but it isn't a direct copy of the old originals.