Depending on the type of "exchange" you're referring to, the most "useful piece" can range from a historical coin to a versatile travel tool.
For a gift exchange (like White Elephant or a "Favorite Things" party), "useful" pieces often fall into practical or consumable categories: exchange
Historically, the most significant "piece" for exchange was the , famously known as a piece of eight . It was a silver coin worth eight Spanish reales and was widely used as the first international currency because of its uniform standard. Useful Pieces for a Student or Travel Exchange Depending on the type of "exchange" you're referring
If you are preparing for a student exchange trip or long-term travel, certain "pieces" of equipment are considered essential for daily comfort: exchange