Who said it had to be a US coin? As for the question, I don't really have an answer. The only coins I can think of that are that big is plate money which doesn't fit the description. @DarkRage666 Do you remember what the coin looked like? Design or country?
Isn't a dinner plate usually 9" in size ? Plus maybe an inch thick? I can't really say I've seen anything like that in a coin in my 66 years.
It wasn't a decorated plate but you are right about the size... It was solid silver from what I knew and it was proof... it came in a set with other large silver rounds... they were all about half the size or less than them
I concur with @Evan Saltis. If you do a Numista search, the only search result for a coin with a face value of $600 is a gold coin from Bermuda. https://en.numista.com/catalogue/in...d=&i=&a=&dg=&m=&f=&t=&w=&u=&g=&se=&c=&wi=&sw=
Saucer size I have seen. Usually privately made bullion that have coin designs. I have also seen elaborate work done in pewter that are large, have a coin theme and can be quite thick.
more like the size of titanic now thats a coin wait more like the longest luxury silver life boat for all the passengers.
I took a look earlier, looking for silver polygonal coins and got that result. The more basic search of silver coins with 600 denominations are 600 baht from Thailand.
This could be it... too bad there aren't any pictures of it anywhere on the internet.. Probably because it was so rare
lunch plates can be anywhere from 4-9" diameter. Saucers are smaller than 4". Dinner plates are 10.5" diameter.
Regardless, it could alternatively be something sold by the Governments of Niue or Vanuatu. Not to mention, the listings on Numista aren't always the most complete when it comes to modern coins.