As Brandon pointed out, you can look at his feedback and see where he purchased at least a dozen (probably more, but they are being sold by the dozen) pitching machine balls with red/blue stitching on at least 3 separate occasions:
http://www.ebay.com/itm/180870303358
http://www.ebay.com/itm/180847616426
http://www.ebay.com/itm/150751225241
As for why Worth instead of Spalding or Reach, I have no idea. Maybe to differentiate himself from the other sellers foisting all their replica baseballs on the collecting public?
I also find it interesting that he mentions in every listing how he marks the balls with his initials and date to prevent fraud, yet doesn't show them in any of the photos (unless they're so "unobtrusive" that I'm overlooking them?)