In 1975 the Franklin Mint on behalf of Panama released a very special Limited Issue Simon Bolivar Silver Proof 9 Coin Set.

Included in the set is the Simon Bolivar 20 Twenty Balboa Silver Proof Coin struck in solid .925 Sterling Silver weighing 129.50 Grams first issued in 1971 and was the largest legal tender Silver coin in the world, Vasco Nunez De Balboa $5 Silver Proof Coin weighing 35.12 Grams and the Belisario Porras $1 Silver Proof Coin weighing 28.73 Grams all struck in solid .925 Sterling Silver and the remaining coins the 50 Centesimos down to 1 Centesimo are Cupro-Nickel.
These legal tender coins have been struck to proof quality using specially prepared dies and highly polished blanks.