Ok here is what the CP means. In Pampanga, there was a famous katipunan leader during the Philippine-American war. Like the more famous Bonifacio, he was known for carrying a bolo in battle, but since he was only a provincial hero, he is not more well known. Anyways, that hero's name was Carlos Pedrosa, and so the CP is a stamp in remembrance of him.
Ok, now if you bought that answer I have a bridge in Brooklyn that I can sell you for a real good price
Im sorry I couldnt resist the little joke. Just to clarify the above story is completely false. Ive noticed two letter markings on a number of different bolos. I believe Ive also seen the AR combination as well. I think Tom is probably on the right track, and it is a regional mark. I know these marks have always struck me as similar in look, in the type of bolo marked, and just vibe as those more ubiquitous stamps of "Philippines" or "Negrito Phil". Perhaps these newer infamous marks are decendents from this practice? It is interesting to see it popping up mostly on Luzon bolos (for some reason I seem to be remembering seeing central bolos on occaision with similar marks, but have no research files to reference on bolo)...? Zel you got some ideas on the significance of the mark, aside from random regional/makers mark?