Saxon,
It was an assumption that the circled triangle marking, found on Mauser 1910 pocket models, is indication of a Portuguese contract by Roy Pender in his book "Mauser Pocket Pistols 1910-1945. The assumption was based on similar markings found on Portuguese lugers. Since Pender's book was published many Mauser collectors have searched for evidence to prove this assumption but the volume of examples with the markings seems to be proof that the marking has some other meaning. Still many still refer to the marking as a Portuguese contract. I have come to refer to the marking simply as the "circled triangle" and group it with the other rear frame markings that are found on the .25 caliber pistols. I have a theory about these markings but currently no proof to prove it. The other markings you describe are most likely production/inspection markings placed by factory workers indicating the stamped part meets tolerances or passed an inspection.
Regards,
