1966 was the last year for Panama to have a new 90% silver dollar in circulation and in 1967 the silver dollar was only found in the proof sets so I wondering what if the 1964 Peace dollar was released into circulation would 1966 be the last year for a 90% silver dollar to be in general circulation? Also since the Panama silver dollars were minted in the United States were they minted on blanks intended for the Peace dollar?
Most coins minted at any of the US Mints were minted on platchets or blanks that the country had set standards on for said country. So to my knowledge the goverment of Panama would of set the size weight etc... then arrange to have the blanks made to their specs. You can check weight, diameter, and other such items by researching that country coinage. Then compare it to US standars
All of the Panama and Bahamas coins are 1:1 with the US dollar, and the same size and weight. Their coins fit our vending machines, parking meters, tolls. For example the Panama 25 centavos coin is the same size weight and value as our quarter. Dollar and halves might be different, but those specs 38.1/ 26.73 are the same as the Peace dollar.
They were also made by the Canadian mint and Franklin mint ( US Private) from 1966 -1984. https://coinsite.com/panama-one-balboa/ I believe the blanks were being supplied by companies outside of the mint by the 60s, but the GSA had many silver dollars in the vaults before they had their sales, so that would not have been a problem. They would have made restrikes like some privates do today.