That level of knowledge is above my pay grade, but good to know! Perhaps they had some old cases lying around the shop and finally got around to using them. I've encountered similar mix and match situations with late 30s - early 50s Kaywoodies.
The narrow issue here that has intrigued quite a number of what might be called Dunhill pipe antiquarians-- is what the rules might have been about English merchants' use of royal warrants, and the specific details of what they were obligated to do when a monarch who'd publicly endorsed them died.
Whatever else, Dunhill makes it clear they (ie the rules and/or their enforcement) must have been pretty fuzzy.
My own working hypothesis has been that the authorities must have been pretty tolerant about allowing companies to use up everything and anything already on hand (and that moreover since it requires some time for a new monarch to dole out brand new warrants to whomever was chosen to regularly supply a vast number of products and services, there had to be a transition period).
Accordingly, my guess is that stationary, for example, could be fairly rapidly and economically changed to "the late King George" and then to "by appointment to Queen Elizabeth." On the other hand, I'd also guess by 1957 Dunhill's expensive leather "Ventage" cases (handcrafted individually to perfectly fit individual pipes) would have been very slow to sell, and the white silk lining printed prior to 1952 were used, accordingly, at an almost glacial pace.
70 years after the fact, I fear hopes have rather dimmed for a Dunhill inside man to chime in with first hand knowledge of what in fact Dunhill did or why. On the other hand, it may still be possible to ascertain what they were
meant to do. . . .