Most likely they are. I lived in Japan when I was a young girl and cultured pearls were one luxury available for a very modest sum at that time. I used to spend my allowance at a little stall where for a small sum a vendor would open up an oyster in front of you from a large tank and whatever pearl was inside was your's whether perfect, or not white or blue. I have them still in my jewelry box, and had one made into a huge, lovely ring. The post exchanges were a treasure trove of locally produced items, free of the customs fees.

Real cultured pearls, and from the knotted string, a good necklace.

That is definitely the Mikimoto trademark. Pearls are graded on various qualities, just like diamonds. The price of rare metals were also a song, compared to today. One can buy a pretty necklace with less desirable pearls at more modest prices, but Mikimoto sold only fine ones. It would still not have been a cheap purchase even in the sixties, given the wages then. Somebody loved you.

Calliope, that is such a sweet thing to say! Put a smile on my face.

I would imagine the value is lessened by not having the box or certificate anymore, but I will still treasure it.

Thanks everyone for responding.

Look closely to see if there are any hallmarks on it pertainingto the metal. Mikimoto usually used white gold.

Calliope: At first I thought this was a clue that it wasn't a real Mikimoto. Then I did a little research and found out that they indeed used silver during the late 60's. And on the clasp below the "M", it says SIL. I know most of Mikimoto's are gold, but since DH purchased this during the time they used silver, maybe it is real. Well, low end for a real one, but still real. Still not 100% sure, but leaning that way.