If the tubes were made with acid etched codes as were all the Philips Europe tubes then the code is all that matters. Same can be said of the silk screened codes, but they can be more easily faked and often rub off. Branding has no influence on the quality of the tubes. This is especially true of the major electronic companies like Magnavox or Philco. A rebranded Amperex made Mulllard is just as good at the Amperex branded tube. If it is a rebranded like National, I guess it is possible that these could be rejects.
I have experienced differences in sound from the same tube with different production dates from the same mfgr. I would attempt to get identical or very close production dates especially in high quality 2 channel applications.
In closing look to things like the Telefunken diamond, acid etched codes, tube seams or top dimples when buying old stock tubes. Look for things that are difficult to duplicate. One more thing that buyers seem to get hung up on is the quality of the tube lettering. On many tubes, the lettering can be easily rubbed away. What you dont want to see is the lettering that wont wipe off easily. If the lettering is fixed or yellowed this tube has most likely seen heat.