Wow! Look at this beautiful coin from Stack's April 2010 Coin Galleries Sale. It sold at auction for $757 US dollars, a completely fair price (maybe too fair) for such a beautiful piece. Not only is the coin beautiful, with a deep, sharp strike and attractive toning, it is housed in an NGC numismatic holder. All these attributes add to value.
A scudo is 140 soldi, shown at the bottom of Stack's picture. Lynn's coin is a half scudo, with a 70 at the bottom. Quarter (35) scudo are another denomination. In general, the smaller the denomination, the lesser in value.
Francesco Erizzo was Doge in Venice from 1631 to 1646. Doge is a political term, an office of prestige and power.
Retail prices for such coins range from a few hundred dollars to $1000. The largest determining factor is the condition of the coin. CoinQuest thanks Stack's for releasing copyright on this picture, because it is such a fine example of this rare piece. Coins with more wear and less eye appeal will end up at the lower end of the price range.
If you are selling a coin to a dealer, or putting it up for auction, remember that there will be a mark-down from the retail prices cited above. Mark-downs in the range of 30 to 50 percent are typical.