I always seem to neglect combining the obvious closeness in these sword forms as to Portuguese as well as Spanish, Nando. I try to defer from the use of the term Iberian as I know it sort of annoys you
In many cases it seems indiscernible without specific marks or inscriptions, but in both cases I have only the highest regard for these fascinating arms in either instance, as you know.
I always am so grateful for the notes you share out of these references such as the fine work of Mr. Nobre as these references are quite little known in the scope of published arms material. I agree there may be a degree of regional preference with use of the scallop shell in decoration, but it seems widely diffused overall as these are even quite notable among many espada anchas in New Spain. Since the symbolism is of course certainly and profoundly associated in the Catholic Faith it seems understandable that it may be widely used in many contexts.
Im right with you on these strange, arcane arrangements of letters, and I spent hours going through Wallace Collection and others. The use of interpolation of occult or arcane symbols within these groupings of letters as well as in inscriptions or names seems to have been a trend from Italy an Spain picked up on by innovative German smiths as well. It seems that these groupings in most cases I found are repetitive, one case had for example the letter 'M' repeated five times. With that considered, it seems quite possible that numerology could be in place, but of course those speculations are far beyond any hope for confirmation.
The thing with such arcane symbolism and its inherent secrecy is that obviously there is no documentation which would explain it, and the known meanings intended at the time were lost as those using them passed .
The best hope we have is that cross instances might be discovered which might reflect some consistency with other detail and clues. Here I would join you in hoping that Jasper will come in on this as his experience with these arms is remarkable.