Everything considered, the greatest likelihood (i.e., 99.9%) is that they are cultured pearls. If the clasp is original, it is consonant with good cultured pearls of the period. A triple strand of natural pearls, something beyond rare, would rank large diamonds and probably a significant emerald, given its South American origin.
The two things that pique my interest, as a natural pearl fanatic, are the size and appearance of some of the smaller pearls, and your mention of very fine drill holes. However, you also mentioned they are cold all the time. Coldness/heaviness is more characteristic of cultured pearls, as the central mother-of-pearl bead is denser than actual pearl nacre.
I first would try a good local resource, like Birks. Testing a triple strand at GIA is very expensive, and may not be necessary if someone with experience can look at them first (wish I lived closer, as I would be very curious to see them!). If you can't find someone, and it is true that EGL in Vancouver has a pearl machine now, you might try them. You can ask for a pregrading on just one of the strands, which would be the least expensive option. Another advantage would be not having to deal with international mail, customs forms, etc. Within the US, registered mail can be insured up to $25,000, but that is not available to Canada -- the limit is $44! Go figure!
