The online publication "Kodak Safelight Filters" (TI0845} has graphs for 14 filters but no OB. The older and very comprehensive paper book "Kodak Filters for Scientific and Technical Uses" (B-3) has graphs for 18 safelight filters but still no OB. My copy is the 3rd edition from 1981.
Andy, could this be a really old filter? Perhaps if someone has the first edition of B-3, it might have the info, or an older edition of the CRC Handbook.
Probably OB is in between OA and OC in its properties. The shapes of the transmittance curves are similar for the OA and OC filters. The OA filter transmits more light in a broad band around 600 nm than does the OB. If the OA is suitable for your paper, then probably the OB will be. But as always, you should test, because it depends on your specific setup. And if the filter is used, it might be faded.