As with all gold coins, a good place to start is with the melt value. That's the value you would have if you used a blowtorch to melt your coin into a pool of liquid gold (don't you dare do it!).
For Argentinian 5 Pesos, there are 0.2334 troy ounces of pure gold in each coin. At today's high price near $1100 US dollars per ounce, that's 0.2344 x 1100 = $258 melt value. Use Kitco.com or a similar web site to get the current gold price.
But your coin is worth more than melt. It has numismatic (coin collector) value as well. For your coin, assuming it is free of problems like stains, spots, dents, and cleainings (NEVER CLEAN A COIN ~~ CLEANING RUINS VALUE) the numismatic value is about:
worn: add $25
fully uncirculated: $add 120
You describe your coin in very good numismatic condition, so our best shot at value is $258 + $75 = $333. This is an approximate retail value you would pay if you were buying the coin. If you were selling it, the buyer would want a margin, say $50, which would bring the value down to $333 - $50 = $283.
For a lengthy explanation about buying and selling gold coins, please click to this CoinQuest link.