The bowls are made of bell metal bronze. The older bowl - on the right - plays in the note of A for the third eye chakra while the modern bowl - on the left - plays the note of D for the sacral chakra.
It takes four members of the clan up to 40 hours to make smaller bowls and up to 1,200 hours to make larger bowls. As they hammer the bowl, they chant sacred mantras to infuse the bowls with energy. They never know what note the bowl will sound until it reveals itself when it is complete.
I found the bowls in a little shop in Old Town San Diego called Gum Saan Land of the Golden Mountain. The owner, Casey, is a sound healer who is passionate about his work. He travels to Nepal to hand select items for his shop, including each of the bowls. I saw video of modern bowls being made by the clan - and it is amazing.
If you happen to be in Old Town San Diego, I highly recommend stopping to see Casey at Land of the Golden Mountain and seeing all the treasures he brings back. He is knowledgable and passionate about what he does.