Hello everyone and thank you for your replies.
Thank you for the link. One of the first things I did when this arrived and I found the words carved into the hilt was to do a google search on them and the link you posted was one of the first that I checked out.
Yes, the hilt is of worn horn
and I am very happy to hear you think it might be pre 1900. To answer your question "Where do you keep coming up with this stuff?" believe me when I say it is purely by accident or just plain dumb luck, I'm not sure which.
Like Jose I have never heard of Balayong wood. The color of this wood is very dark, almost like teak but with like you say "a deep purple color" to it. It looks more reddish in the photos because of the flash.
Now if someone can tell me the meaning of the words carved into the hilt I would be happy.
I know from the Wikipedia link mentioned by Rick that Apalit is a municipality in the province of Pampanga and was supposedly named after the Apalit tree also known as the Narra the National tree of the Philippines. (This is something I had not known before but interesting none the less.) I do not know if PAMP is supposed to represent Pampanga ? After looking at the carving SON in sunlight with the help of a magnifying glass I think that there might be one more letter "though it is worn almost completely away" that might be an S making the word SONS ? Castro I am guessing might have been the owners name or the writing in total might be a tribute to that person?
All help will be greatly appreciated.