In modern minting technology, a planchet is a coin blank that is fed into a machine where it receives the coin pattern when struck at high pressure between two coin dies. Usually blank planchets are upset prior to striking. That is, they receive rims before entering the striking machine. The blank planchet in our picture is for a US Lincoln cent.
Daniel has a blank planchet for a Canadian Loon dollar, found at this link on CoinQuest. You rarely hear them called 'loon dollars' in preference to the endearing 'loonie.'
The problem with blank planchets is that one is not often sure where they come from. In Daniel's case, it is a blank loonie for sure. But proving that may be difficult. A genuine loonie weighs exactly 7 grams, and this helps in identification.
Most blank planchets run between $2 and $10 US dollars retail when they are unidentified. When completely authenticated and identified by a major numismatic service, such as PCGS, NGC, ICG, or ANACS, blank planchets can tip the scales at $200 or more.