At first glance: It looks like a cultured pearl to me.
It's very nice!
Remember that cultured pearls make up about 99% of all pearls on sale...so, just with that in mind it would be rare if you have a natural pearl.
Hi! I want to sell it but I don't have any evidence that it's a natural pearl. They're looking for a certificate but I think there is no laboratory for pearls here in the Philippines. Can I have some advice on what should I do or where can I get a certificate for my pearl in the Philippines?
I would send it over to the Bangkok GIA lab. It's the closest you have for this service.
BUT before you do: try to find a local dentist with good x-ray equipment. Bring 2 pearls, one cultured (that you fully know is cultured) and this pearl you want to analyze, and have them x-rayed.
This is how cultured pearls would look like using a Dentist's x-ray apparatus. All these pearls were analyzed because they were supposed to be "natural pearls". You can clearly see the bead inside.
All those in the photo are cultured. And they were all SUPPOSED to be NATURAL, so, my friend Edgar took them for x-rays...and nice surprise! They came out as CULTURED.