I cant upload a picture of the pendok right know but it is the same colour as this panchaloha statue, not as yellow as brass but not as rich/golden as gold. It hasn’t tarnished unlike a brass pendok. There is nothing special about the construction of the pendok itself, actually very plain.
I have seen a metallurgical analysis of antique Tibetan singing bowls and it demonstrated that they were made from a complex alloy which contained also quantities of gold and silver.
My understanding is that they were (not modern ones) made from five metals (panchaloha) and westerners made up this concept of them being made of seven metals to fit their own understanding i.e. one metal for each planet.
Just consider the addition of quicksilver to represent the planet mercury and you will know it is impossible i.e. it will boil off before the other metals are even red hot filling the room with mercury vapor
http://en.wikipedia.org/wiki/Panchaloha