pawn shop
You can sell it on eBay or take it to a coin collector.
Check that coin again. The first year for buffalo nickels was 1913.
Each 100 Pesos coin contains .6429 oz. of actual Silver weight. They currently sell for around $13 in almost uncirculated condition.
The coin is worth around $50.00 bucks (depending on silver price). If anyone tries to sell it to you for more than 20 spot on silver its a rip.
It is a common coin and usually worth the melt value of the silver content, which is approximately .39 ozt. At this time the approximate value is about $13-$15. If the coin is in extraordinary condition it may be worth a little more. Check Ebay auctions to see what this coin is currently selling for.
To a collector, presumably, it would depend on where / how you're trying to sell it. I believe more than one country uses the "peso" and that would help. Look through the numismatic indexes, I would suggest.
This is one variation of the magician's coin where one coin is hollowed out and the other cut down to fit inside. Usually sell for $5-$10 in novelty shops or $2-$3 on eBay.
You could sell them at a coin store, eBay, or bring them to a coin show. And find out what there worth.
10000 pesos 10000 pesos
As I don't live in Arizona, I can't really help you find a coin dealer there. However, the gold 50 peso coin contains 1.2057 troy ounces of gold and is worth about $1,690 in gold content alone at the time of writing. Beware of "cash 4 gold" style people who offer low. Rather, I would try to find a coin dealer of jewelry shop that deals in precious metals. Alternatively, sites such as the American Precious Metal Exchange (APMEX) will buy some coins and is currently offering $1,687.32 for gold 50 peso coins. However, I have not used APMEX and I would find out more information about them and their policies before I would sell to them.
A peso is about 10 cents. So in a pawn shop it would probably be a couple of pennies.
99 pence