Hey, that's a neat coin, isn't it? The good part is that it is made of silver, 0.362 troy ounces, to be precise. The coin commemorates the Sesquicentennial (150th anniversary) of the Revolution against Spain. Gaucho is an equivalent of the North American cowboy, the Chilean huaso, the Cuban guajiro, the Venezuelan or Colombian llanero or the Mexican charro.
Finding the value of these coins takes a little work. First find the base value (BV) of the coin by multiplying the current price of silver (look it up at kitco.com, it changes every day) by 0.362. At the time of this writing in December 2013, silver is trading at $19.27 US dollars per troy ounce, so BV = 0.362 x 19.27 = about $7.
Once you have the BV, add a little value for coins in better condition, as follows:
worn: value is BV
average circulated: BV
well preserved: BV + $2
fully uncirculated: BV + $8
These figures are about what a collector would pay to buy this coin. If you are selling your coin to a professional dealer, he or she must make a profit to stay in business, so expect offers around one-half to two-thirds of these values.