Good confusion Nando!
and I think we need our deerstalker hats and pipes!
I had not dragged out my copy of Gyngell as it was more buried than the rest. I think what we need to remember on these references on markings is that they are primarily compendiums of marks gathered off various examples of arms collected and in museums. There is of course no structural data in most cases as far as biographical or other data, though Wagner, Mann and some others will offer some detail in texts.
I think the most important thing we have revealed here is that there were some clearly preferred or more commonly used choices with the German makers, and apparently some more comprehensive uses of punzones by the Spanish makers then thought. Most collectors like to see things neatly classified and categorized, however using the reality factor, there are probably more exceptions than rules.
The 3 might have had several explanations which will remain elusive as far as actual intent. It could of course be religious, as in Trinity....or magical as well known in the occult climate well established in Spain. To me what has been most interesting is the commonality of the joined S and T as used by both Spanish and German makers.
I am wondering if perhaps Pedro/Pietro might have been an amalgamated persona with Solingen origins in the manner of ANDREA FERARA and TOMAS DE AIALA as well as SAHAGUM in a brand sense. Possibly this is why this person does not appear in the Spanish chroniclers records.