There is only one 'Boxpok' (it was a copyrighted tradename). There are a couple of technical variants in the coring (for example, for different styles of counterweight provision, and a pocket for those roads that used cross-balance weighting at 90 degrees) but the general appearance of the drivers was common.
Some of the disc centers were not cast, but fabricated. The general subject is discussed in some respects in the relevant sections of contemporary Locomotive Cyclopedias. Here is an illustration in a recent thread on another forum that shows some differences:
To my knowledge all the B&O disk drivers applied to the P7s were GSC Boxpok - unlike the NYC switching between Boxpok, Scullin disc, and Web-Spoke cast centers in the latter years of the J3a Hudsons. I found it interesting that 5304 had a full set of Boxpoks during and after the Kuhler streamlining, but these were replaced with spoked drivers when the Olive Dennis Cincinnatian streamlining was installed...