Jim, if you allow me, you are a master researcher and your conclusions must be taken into decisive account but, as you well mention, you might (only might) have it.
The marks that are shown in Wallace A595 ... and eventually A596, are precisely the same as shown by Gyngell ... as if they had the same printing origin and, as you well know, have no slight resemblance with the one seen in Norman's blade. As i ignore Kinmans's work (from which i would like to have a copy) i am compelled to accept the allusion to the horizontal crowned IB
. I take it that such is only a written description, that not an actual design of the mark. A pity we can not see such cartouche; the IB
font in Norman's blade is 'so strict', when compared to the (sort of) Italic B
applied in the marks currently disposed. Not to speak that the blade in Wallace A595 is so distinct from the one discussed here, as they were forged by different hands but, that is another deal.
Pay not much attention to my inconsistent approach, as i obviously stand to b corrected.