I only have one medio Balboa.. 1979. Many of them are produced by the U.S. mint and have the same specifications as U.S. coinage. They're interesting. Too bad, mine isn't an earlier one made of silver.
I found one of those in January. Neat picture on the coin I guess... it ended up in the foreign box with all the strange dime size coins I have found. I think mine was from 1982 also.