Coinage Help

[Mehman]

I'm trying to find the weight for an electrum coin worth $200 using DF Treasures 1 and Pyramid 3/119 After the End II. I'm truly stumped. (My wife is stumped, too, so I know I'm in trouble.)

What I'm looking for is the weight in ounces to convert to pounds to find the count/pound and also figure out the diameter of the coin. Ideally, I'd like to know how to figure out the coin's composition, too. (It's a 1:1 Au:Ag electrum, nothing fancy.)

The example given in 3/119 After the End II on p 36 is helpful, but I don't know the final weight of the coin. All I know is that I need an electrum coin worth $200.

If someone can help, I'm obviously not great at math - simple terms please.

(I tried searching the forums, but my search-fu failed me.)