a blast furnace
You can exchange a 1991 $20 Canadian paper bill at most banks and credit unions in Canada, as they typically accept older currency for deposit or exchange. Additionally, some currency exchange services may also accept it. If you're outside Canada, check with local banks or currency exchange services that deal with Canadian currency. Keep in mind that you may receive the current value rather than the face value if it is considered collectible.
Currency is something people are willing to accept in exchange for goods or services. Dollar bills and coins are example of currency. Most people will not accept notebook paper in exchange for providing a good or service, and thus it is not considered currency.
The official exchange of Deutsche marks has come to an end. However, you can still take your old German currency to the Bundesbank (Germany's Central Bank) and exchange it for euros. Most currency exchanges (banks, airport exchanges, etc.) will only buy currency that is still in general circulation. Specialized currency exchanges such as Euro Coin Exchange (http://www.webuyeuros.com/germany) will buy your old marks, and you can get paid in dollars without having to ship your cash to Europe.
Exchanging 500 paper money pesos from 1981 into US dollars is unlikely to be possible through conventional currency exchange channels, as these pesos are no longer in circulation and may hold little to no face value. Their worth may instead be determined by collectors or numismatists, depending on their condition and rarity. If you're looking for a financial exchange, it's best to check with specialized currency dealers or auction platforms.
either gold or silver
American currency, with the paper bill currency called dollars or sometimes 'bucks', and the coin currency called cents.
100000
"Currency' is money in any form when in actual use as a medium of exchange, especially circulating paper money.
european architecture and windows
$61 dollars in modern day US currency.
There will be an established exchange rate and you can probably find a bank that does exchange to get Canadian money for your Mexican money.
bimetallism