I would be very surprised if that was the case, considering how large the letters are. The big letters on milk bottles that I've seen have only ever been the initials of the dairy or its owner. They were used for quickly checking whether any of their competitors' bottles had gotten mixed into their supply by accident, so that people at the plant didn't have to rotate each bottle and read the embossing to make sure it was one of theirs.I'm pretty sure BB stood for Berney-Bond Glass Co. Here in RI, the old milk bottles had the seal markings, and RI BB Seal meant Berney-Bond Glass Co.